"Moreover the strangers … will I bring to my holy mountain, and make them joyful in my house of prayer … for my house shall be called an house of prayer for all the peoples" (Isaiah 56:6-7). The invitation of this Psalm corresponds to the prediction of the prophet: and the series of anthems for the dedication of the restored Temple which begins in Psalms 95 with a call to Israel to worship ends fitly with a call to the whole earth to join in Israel's worship, acknowledging Jehovah as the only true God, Whose claims upon the allegiance of the whole world have been attested by His recent mercy to Israel. Psalms 100:1-2; Psalms 100:4, are an echo of Psalms 95:1-2; Psalms 100:3 of Psalms 95:7; and parallels to most of the language are to be found in the other Psalms of this group.
The liturgical history of this Psalm is of special interest. The title should probably be rendered A Psalm for the thankoffering (R.V. marg.), rather than simply A Psalm of thanksgiving(R.V.). It refers to the use of the Psalm in the Second Temple in connexion with the sacrifices of thanksgiving (Leviticus 7:11 ff.). For similar notices see the titles of Psalms 38, 70, 92. The general character of its contents makes it probable that it was not specially written for the purpose, but adopted on account of Psalms 100:4.
From ancient times it has been used in the daily service of the Synagogue, except upon certain festivals. It was used in the early morning service of Lauds, and at the revision of the Prayer Book in 1552 it was added as an alternative for the Benedictus. The metrical version of it, universally known and loved as the "Old Hundredth" (i.e from the oldVersion of the Psalms by Sternhold and Hopkins), first appeared in the Psalter published in London by John Daye, 1560 1, and in the Anglo-Genevan Psalter, printed at Geneva in 1561. Its author is believed to have been William Kethe, a native of Scotland, who was forced to fly during the Marian persecutions, and joined the exiles at Geneva in 1556. The tune is found in the French-Genevan Psalter of 1551 as the tune to Psalms 134. See Julian's Dictionary of Hymnology, pp. 43, 44.