The over-all message of Psalm 50 is actually a rebuke upon the Religious hypocrite who is determined to ACT OUT VARIOUS religious rituals, but refuses to offer God the Thanksgiving-Glory due Him. The Psalmist Asaph is warning the hypocrite to mend his ways by reflecting upon the UNSEEN Saviour Who is only SEEN by the eye of Faith.

While the hypocrite is able to perform outward works, in a show of religious observances, he is unable to manufacture sincere gratitude for the work of Grace. He is unable to be sincerely thankful for the various Providences that have blessed him and guided him throughout his life, simply because he has not actually experienced the work of grace.
This Psalm is a wake-up call for all of us, who have reaped an abundance of God’s Blessings, and yet remain in a posture of murmuring and discontentment.

Jonathan Edwards notes that…

“Affections that are truly spiritual and gracious…arise from those influences and operations on the heart, which are spiritual and Divine.” Religious Affections p 197

According to the puritans, Edwards and Thomas Shepherd, Asaph the Psalmist is exposing two kinds of hypocrites; the Legal and the Evangelical.

Edwards observes,

“There are two sorts of hypocrites: the first, are deceived with their outward morality and external religion… The other, are those that are deceived with false discoveries and elevations, which often cry down works, and men’s own righteousness, and talk much of free grace, but at the same time, make a righteousness of their discoveries, and of their humiliation, and exalt themselves to heaven with them.

These two kinds of hypocrites Mr. Shepherd, in his ex-position of the Parable of the 10 Virgins, distinguishes by the names of legal and evangelical hypocrites, and often speaks of the latter as the worst. And ‘tis evident that the latter are commonly by far the most confident in their hope, and with the most difficulty brought from it.” Ibid P173

Asaph identifies the first hypocrite as one that is deceived by the keeping of outward ceremonies in verses 9-13 he is the legalist.

Ps 50:9 I will take no bullock out of thy house, nor he goats out of thy folds. 10 For every beast of the forest is mine, and the cattle upon a thousand hills. 11 I know all the fowls of the mountains: and the wild beasts of the field are mine. 12 If I were hungry, I would not tell thee: for the world is mine, and the fulness thereof. 13 Will I eat the flesh of bulls, or drink the blood of goats?

In these verses Aspah identifies the Evangelical moralist, who is actually an antinomian, who relates to the Covenant of Free Grace, but is void of true Love toward God by not being thankful. That is the test of sincere love and appreciation toward God. i.e. A thankful heart.

Asaph continues to explain.

Ps 50:16 ¶ But unto the wicked God saith, What hast thou to do to declare my statutes, or that thou shouldest take my covenant in thy mouth? 17 Seeing thou hatest instruction, and castest my words behind thee.

Asaph tells both of these hypocrites in verse 14 to…

… Offer unto God thanksgiving; and pay thy vows unto the most High…

The problem with the hypocrite is that he holds onto a false hope, and a false confidence that he is one of God’s Elect.

Again Edwards observes.

“When once a hypocrite is thus established in a false hope, he hasn’t those things to cause him to call his hope into question, that often times, by the occasion of the doubting of true Saints. At first, he hasn’t that cautious spirit, that great sense of the vast importance of a sure foundation, and that dread of being deceived. The comforts of the true Saints increase awakening and caution, and a lively sense how great a thing it is to appear before an infinitely holy, just in of mission to judge. But false comforts put an end to these things, and dreadfully stupefy the mind. Secondly, the hypocrite has not the knowledge of his own blindness, and the deceitfulness of his own heart, and that mean opinion of his own understanding, that the true Saints has. Those that are diluted with false discoveries and affections, are ever more highly conceded of their light and understanding.”

Drawing from the Law of God in Leviticus 7:12, Asaph reminds the hypocrite that a

Thankful Posture’ is an essential component when offering up the required ceremonial scarifies of Peace, and that thankful posture does not exhibit itself ONLY when things are going well. Thanksgiving is the posture of the True Saint at every season.

God is, however, very clear in that this Peace offering was to be offered WITH Thanksgiving otherwise it would not be an acceptable offering. Whenever contemplating the Peace Treaty, which God had CUT with Israel, the people were to be Thankful. A sincere heart of thanksgiving was what yoked the sacrifice with the people and which made the sacrifice acceptable.

Ro 8:28 And we know that all things work together for good to them that love God, to them who are the called according to his purpose.

Rev George Barlow comments,

1Th 5:16 ¶ Rejoice evermore.17 Pray without ceasing.

And for the record, (to reiterate) a Thankful heart does not show itself in giving thanks once

in a while, over the dinner table or in private devotion, or when things go well, but rather the thankful heart is FILLED WITH Thanksgiving at all times. Thanksgiving is the exercise of love and faith for all that God is and in all that God does. God impresses this ROOT of LOVE in the declaration of the Great Commandment, knowing that LOVE is the well spring of all other affections which is inaugurated and fed by the indwelling of God, the Holy Spirit.

1.    First. Thanksgiving out of a pure loving heart is the Christian’s DUTY
It is the WILL and thus it is the Commandment of the Sovereign King that you humble yourself and bless Him by Thanking Him. 
It is the WILL and thus it is the Commandment of the Sovereign King that you humble yourself and bless Him by Thanking Him.

Those who honestly and sincerely thank God, do so out of the Spirit’s prodding – and it is of the highest privilege to be moved by the Spirit of God. Whenever we thank God, it is because He has given us something that was not part of our being to begin with. The privilege is that we have been given something from GOD!!!! 
Think of it. God has given you something that you didn’t have before and moreover that you never deserved in the first place. A heart to love Him, Thank Him, Praise Him, and Pray to Him.We have God as our God and Father. He is also the Universal King of the Universe. HE gives only to His Own, conferring upon them a great honor which IN TURN Thanks Him for such a mercy.

The beginning of Wisdom is the Fear of the LORD. That fear is an honoring and awe inspiring aspect of the saint. This impresses upon the mind of the Christian exactly WHO GOD is, and what is commanded of him for his own benefit. AND so it is in the saint’s best interest (in His wisdom ) To Give Thanks to the Lord.

Moses explained to Israel that obedience to the Commands of God was WISDOM.

De 4:5 Behold, I have taught you statutes and judgments, even as the LORD my God commanded me, that ye should do so in the land whither ye go to possess it.

 IN Psalm 105 the Psalmist sets Thanksgiving as a PREREQUISITE to calling on God for His Help and Deliverance.

Knowing that God is well pleased with Thanking Him, that knowledge in and of itself is an Excellency of knowledge and understanding.

Paul tells the Philippians,

Php 3:8 Yea doubtless, and I count all things but loss for the excellency of the knowledge of Christ Jesus my Lord: for whom I have suffered the loss of all things, and do count them but dung, that I may win Christ

The rendering of Thanksgiving is a character dynamic of the Regenerate. It is a Necessary attribute for the Christian without which one remains doubtful of his or her conversion.

It reminds us that He is generous because we are needy. We must be ever so conscious of our need for charity. By accepting our poverty of body, soul and spirit, in light of the Grace that has been given to us, we, out of sincere NECESSITY, give thanks. The Christian should naturally take delight in Thanking God, knowing that God delights in us, when we are sincerely Grateful. As the Apostle declares, and as all of us should likewise declare…

Moses says this.

Le 7:11 ¶ And this is the law of the sacrifice of peace offerings, which he shall offer unto the LORD. 12 If he offer it for a thanksgiving, then he shall offer with the sacrifice of thanksgiving unleavened cakes mingled with oil, and unleavened wafers anointed with oil, and cakes mingled with oil, of fine flour, fried.

The Law is very explicit in what type of sacrifice this was.It was for the Peace offering, which meant it was symbolic of the Peace Treaty between God and His People, according to the Covenant cut with Blood – representing the Lord Jesus.

Paul explains,

Eph 2:14 ¶ For he is our peace, who hath made both one, and hath broken down the

middle wall of partition between us; 15 Having abolished in his flesh the enmity, even the law of commandments contained in ordinances; for to make in himself of twain one new man, so making peace; 16 And that he might reconcile both unto God in one body by the cross, having slain the enmity thereby: 17 And came and preached peace to you which were afar off, and to them that were nigh. 18 For through him we both have access by one Spirit unto the Father.

Whatever was offered – whether it was the cakes mingled with oil, or the anointed unleavened wafers of fine flour – it was UNACCEPTABLEifwas offered without Thanksgiving. Thanksgiving was the main Component of this ceremony of Peace and remains so throughout eternity. It was not so much the material cakes and unleavened wafers that Israel was thankful for, but what those things signified that moved the people to praise and Thank God.

But there was something more to this sacrificial offering. This offering was made with an oath, It was coupled with a VOW. In other words it was a requirement.
Ps 50:14 Offer unto God thanksgiving; and pay thy vows unto the most High

Adam Clarke explains,

“Now these were offerings, in their spiritual and proper meaning, which God required of the people: and as the sacrificial system was established for an especial end; to show the sinfulness of sin, and the purity of Jehovah, and to show how sin could be atoned for, forgiven, and removed; this system was now to end in the thing that it signified,-[i.e.] the grand sacrifice of Christ, which was to make atonement, feed, nourish, and save the souls of believers unto eternal life; [and] to excite their praise and thanksgiving; [and to] bind them to God Almighty by the most solemn vows to live to him in the spirit of gratitude and obedience all the days of their life. And, in order that they might be able to hold fast faith and a good conscience, they were to make continual prayer to God, who promised to hear and deliver them, that they might glorify him, [according to the next verse of Ps 50:15.]..which states: Ps 50:15 And call upon me in the day of trouble: I will deliver thee, and thou shalt glorify me.”

The rendering of sincere Thanksgiving established a spirit of gratitude which WAS REQUIRED in payment of Israel’s oath. Biblical vows, if they were to be valid, had to be voluntary. God is calling on Israel to voluntarily praise and give Him thanks for His fidelity and grace. The VOW was a promise that in everything, the people of God were to ‘Give Thanks’ from the outpouring of gratitude for the LORD and HIS work.

This is the intent of the Apostle when he counsels the Thessalonians.

1Th 5:18 In every thing give thanks: for this is the will of God in Christ Jesus concerning you.

He makes it a point to tell the Thessalonians that it is GOD’s WILL (Which is His commandment) that His people render thanksgiving in everything. Paul is able to say this because he understands that ALL THINGS work together for good.

He tells the Saints at Rome,

“It is our duty to be ever grateful… The Christian can meet with nothing in the way of duty that is not a cause for thankfulness, whatever suffering may be entailed. When we think of the ceaseless stream of God’s mercies, we shall have ample reasons for [uninterrupted] Thanksgiving.”

According to the Apostle Paul the command to give thanks isn’t isolated from the Command to rejoice and pray. He rather enjoins the three together.
Continual Prayer and Rejoicing are also commanded as being part of the will of God

He puts together a kind of Trinity of commands for the benefit and well being of the saints. Rejoicing, Prayer and Thanksgiving.

Observe the connection made between prayer and thanksgiving  when writing to the Philippians and Colossians,

Php 4:6 Be careful for nothing; but in every thing by prayer and supplication with thanksgiving let your requests be made known unto God.

 Col 2:7 Rooted and built up in him, and stablished in the faith, as ye have been taught, abounding therein with thanksgiving.

 Col 4:2 ¶ Continue in prayer, and watch in the same with thanksgiving.

The Rev George Barlow again observes,

“The secret of a happy life is in harmony with the divine will… It is the will of God that his people should be rejoicing, praying, and grateful; and this will is revealed by Christ, as declared in his gospel, as received in his church, and as observed by those in communion with him. What a revelation is this, not of an arbitrary demand of the impossible state of the affections toward God, but a beautiful and consolatory discovery of the largeness of his love and of the blessed ends for which he has redeemed us in Christ. The will of God supplies constant material for gratitude and praise. These are the three marks of a genuine Christian. 1. To rejoice in the mercy of God. 2. To be fervent in prayer. 3.To give thanks to God in all things.” Homiletic Commentary pg 543

If one were to take careful notice of the various Psalms, one would immediately see that there is a powerful and obvious theme throughout; Praise and Thanksgiving for God.

Throughout the Old Testament the Prophets have lifted up the Name of the LORD in Thanksgiving and Praise.

Ps 26:6 ¶ I will wash mine hands in innocency: so will I compass thine altar, O LORD: 7 That I may publish with the voice of thanksgiving, and tell of all thy wondrous works.

Ps 69:30 ¶ I will praise the name of God with a song, and will magnify him with thanksgiving.

 Ps 95:2 Let us come before his presence with thanksgiving, and make a joyful noise unto him with psalms.

Ps 100:4 Enter into his gates with thanksgiving, and into his courts with praise: be thankful unto him, and bless his name.

 Ps 107:22 And let them sacrifice the sacrifices of thanksgiving, and declare his works with rejoicing.

Ps 116:17 I will offer to thee the sacrifice of thanksgiving, and will call upon the name of the LORD.

Ps 118:1 ¶ O give thanks unto the LORD; for he is good: because his mercy endureth for ever.

 Ps 147:7 Sing unto the LORD with thanksgiving; sing praise upon the harp unto our God:

 Isa 51:3 For the LORD shall comfort Zion: he will comfort all her waste places; and he will make her wilderness like Eden, and her desert like the garden of the LORD; joy and gladness shall be found therein, thanksgiving, and the voice of melody.

 Jer 30:19 And out of them shall proceed thanksgiving and the voice of them that make merry: and I will multiply them, and they shall not be few; I will also glorify them, and they shall not be small.

What all these Old Testament prophets were praising and thanking God for, was not only

what He had done in their history, but MOREOVER, IN ANTICIPATION of what He was going to dothrough the LORD Jesus, in all of history. And so when Paul speaks of the giving of thanks, he often focuses upon the aspect of the spiritual and temporal victory effectuated by the resurrected Christ.

1Co 15:57 But thanks be to God, which giveth us the victory through our Lord Jesus Christ.

2Co 2:14 Now thanks be unto God, which always causeth us to triumph in Christ, and maketh manifest the savour of his knowledge by us in every place.

2Co 9:15  Thanks be unto God for his unspeakable gift.

Col 1:12 ¶ Giving thanks unto the Father, which hath made us meet to be partakers of the inheritance of the saints in light.

Re 4:9 And when those beasts give glory and honour and thanks to him that sat on the throne, who liveth for ever and ever,

 Re 11:17 Saying, We give thee thanks, O Lord God Almighty, which art, and wast, and art to come; because thou hast taken to thee thy great power, and hast reigned.

Consider for a moment the ROOT of Thanksgiving

The root of a Thankful heart is LOVE ; a Love Toward God. When the heart is filled with LOVE and Devotion to God, it is reflected in Thanksgiving. This type of Love focuses on God and His Redemption though the Crucified and Risen Lord Christ. Love toward God is expressed in Thanksgiving. There is no other way about it. If you do not have a thankful heart you may not be a Christian.

De 6:4 ¶ Hear, O Israel: The LORD our God is one LORD: 5 And thou shalt love the LORD thy God with all thine heart, and with all thy soul, and with all thy might.

Jesus adds an additional but extremely important nuance to the Commandment.

Mt 22:37  Jesus said unto him, Thou shalt love the Lord thy God with all thy heart, and with all thy soul, and with all thy mind.

The sincere contemplation of the mercy of God with the mind should, result in a brokenness to the point of praise and thanksgiving. This is to be expanded further to include a love toward our neighbor which Jesus declares as the second great commandment.

Mt 22:39 And the second is like unto it, Thou shalt love thy neighbour as thyself.

This commandment teaches us that the hypocrite’s thanksgiving, IF HE SHOWS ANY SIGN OF BEING THANKFUL, only goes as far as himself and not to his neighbor.

Observe the parable of the wicked Hypocrite.

Lu 18:10 Two men went up into the temple to pray; the one a Pharisee, and the other a publican. 11 The Pharisee stood and prayed thus with himself, God, I thank thee, that I am not as other men are, extortioners, unjust, adulterers, or even as this publican.

You see this man VERBALLY gave thanks, but his heart was far from the love of God and love toward his neighbor, rendering his thanksgiving UNACCEPTABLE even damnable.

The Great Puritan Thomas Vincent explains that it is LOVE toward God that excites all other reactions, and in this case Thanksgiving.

He lists 8 considerations for the Christian to contemplate which can be used to encourage and excite the heart and mind to Love and Thanksgiving.

2.    Second: Thanksgiving is a PRIVILEDGE.

3.    Third: It is a great HONORto be able to Thank God.
4.    Fourth: There is also WISDOMin rendering Thanksgiving to God.

 6 Keep therefore and do them; for this is your wisdom and your understanding in the sight of the nations…

Ps 105:1 ¶ O give thanks unto the LORD; call upon his name: make known his deeds among the people.

5.    Fifth: There is also an EXCLLENCYin Thanking God.

6.    Six: There is also the NECESSITYof Giving Thanks.

7.    Seventh: There is also a USEFULLNESSin the giving of Thanks.

8.    Finally, Thanksgiving is A DELIGHTFUL practice.

2Co 9:15 Thanks be unto God for his unspeakable gift.  AMEN