This psalm - so beautiful - so grand - so often sung in all lands and languages - completes this "group" of psalms respecting the reign of God, or the reasons for praise as derived from the fact that he reigns. In the previous psalms in this group Ps. 95-99 the call to praise had been in some respects local and particular; in this, it is universal. All lands are called on to praise him; all people to worship him as God. The "ground" of this, as stated in the psalm, is that he is their "Maker;" that he is the Creator of all. As all have derived their being from him, they are called on to praise him as their common Creator and Father. So far as the reason here referred to is a ground for praise and worship, it applies to all people now. The nations - the people of the earth - are one. However much they may differ in complexion, in language, in customs, in religion, they have all been formed by the same God; they are all of one family; they are all entitled to the same privileges; they may all have the same access to his throne. The races of people are one; and all should gather around the throne of their common Creator, and render him united praise. This psalm has been sung by million and hundreds of million; it will continue to be sung to the end of time.
The psalm is entitled "A Psalm of praise In the margin, "thanksgiving." The Septuagint is, "A Psalm of Confession" - εἰς ἐξομολόγησιν eis homologēsin. So the Latin Vulgate, and the Chaldee. The Syriac version is, "anonymous," or, without a name; "concerning Joshua the son of Nun, when he subdued the Ammonites." Luther: "A Psalm of Thanksgiving."

All nations are exhorted to praise the Lord, Psalm 100:1, Psalm 100:2; to acknowledge him to be the Sovereign God and their Creator and that they are his people and the flock of his pasture, Psalm 100:3; to worship him publicly, and be grateful for his mercies, Psalm 100:4. The reasons on which this is founded; his own goodness, his everlasting mercy, and his ever-during truth, Psalm 100:5.
This Psalm is entitled in the Hebrew מזמור לתודה mizmor lethodah, not "A Psalm of Praise," as we have it, but "A Psalm for the confession, or for the confession-offering," very properly translated by the Chaldee: שבחא על קורבן תודתא shibcha al kurban todetha, "Praise for the sacrifice (or offering) of confession." The Vulgate, Septuagint, and Ethiopic have followed this sense. The Arabic attributes it to David. The Syriac has the following prefixed: "Without a name. Concerning Joshua the son of Nun, when he had ended the war with the Ammonites: but in the new covenant it relates to the conversion of the Gentiles to the faith." It is likely that it was composed after the captivity, as a form of thanksgiving to God for that great deliverance, as well as an inducement to the people to consecrate themselves to him, and to be exact in the performance of the acts of public worship.

INTRODUCTION TO PSALM 100
A Psalm of Praise. The Arabic version ascribes this psalm to David, and very likely it is one of his: the Targum calls it
"a hymn for the sacrifice of thanksgiving;''
and so Jarchi. It is supposed to have been used when peace offerings for thanksgivings were offered up, Leviticus 7:11. The Syriac inscription is very odd;
"concerning Joshua the son of Nun, when he made the war of the Ammonites to cease;''
though it more rightly adds,
"but in the New Testament, when the Gentiles are converted to the faith:''
and indeed the scope of the psalm is to exhort the Gentiles to praise the Messiah, to serve and worship him, from the consideration of his goodness and mercy, truth and faithfulness.

An exhortation to praise God, and rejoice in him.

Call of All the World to the Service of the True God
This Psalm closes the series of deutero-Isaianic Psalm, which began with Ps 91. There is common to all of them that mild sublimity, sunny cheerfulness, unsorrowful spiritual character, and New Testament expandedness, which we wonder at in the second part of the Book of Isaiah; and besides all this, they are also linked together by the figure anadiplosis, and manifold consonances and accords.
The arrangement, too, at least from Psalm 93:1-5 onwards, is Isaianic: it is parallel with the relation of Isaiah 24:1 to Psalm 13:1. Just as the former cycle of prophecies closes that concerning the nations, after the manner of a musical finale, so the Psalm celebrating the dominion of God, from Psalm 93:1-5 onwards, which vividly portray the unfolded glory of the kingship of Jahve, have Jubilate and Cantate Psalm in succession.
From the fact that this last Jubilate is entirely the echo of the first, viz., of the first half of Psalm 95:1-11, we see how ingenious the arrangement is. There we find all the thoughts which recur here. There it is said in Psalm 95:7, He is our God, and we are the people of His pasture and the flock of His hand. And in Psalm 95:2, Let us come before His face with thanksgiving (בּתודה), let us make a joyful noise unto Him in songs!
This תודה is found here in the title of the Psalm, מזמור לתּודה. Taken in the sense of a "Psalm for thanksgiving," it would say but little. We may take לתודה in a liturgical sense (with the Targum, Mendelssohn, Ewald, and Hitzig), like ליום השׁבת, Psalm 92:1, in this series, and like להזכיר in Psalm 38:1; Psalm 70:1. What is intended is not merely the tôda of the heart, but the shelamı̂m-tôda, תּודה זבח, Psalm 107:22; Psalm 116:17, which is also called absolutely תודה in Psalm 56:13, 2-Chronicles 29:31. That kind of shelamı̂m is thus called which is presented על־תודה, i.e., as thankful praise for divine benefits received, more particularly marvellous protection and deliverance (vid., Ps 107).