Blessed are the sons of God. J. Humphreys. [Christian Privileges.] This is the first of six hymns added by J. Cennick to Pt. ii. of his Sacred Hymns for the Use of Religious Societies, Bristol, F. Farley, 1743, No. 72, p. 95. It is in 8 stanzas of 4 lines, and is headed, "The Priviledges of God's Children." Concerning these six hymns J. Cennick says, "These were done by Mr. Joseph Humphreys." In Whitefield's Collection, 1753, it was given as No. 14 in that part of the collection devoted to “Hymns for Society, and Persons meeting in Christian Fellowship." As shortly after this date it fell out of use in its original form, and the text is somewhat difficult to find….
The Rev. R. Conyers published in his Collection of Psalms & Hymns, 1st edition, 1767, as No. 84, the hymn in a new form. Dealing with the hymn as an unbroken poem of 32 lines, he took the first 6 lines, added thereto the last lines of the hymn as altered by Whitefield ("With them," &c.) as a refrain, and constituted them as stanza i.; the next 6 lines, with the same refrain as stanza ii., and so on to the end, thus producing a hymn of 5 stanzas of 8 lines. Toplady, in his Psalms & Hymns, 1776, No. 116, adopted Conyers's idea of using the last two lines of the hymn as a refrain, by adding them to Humphreys's stanzas i.-iv., vi., and v., in the order named, and thereby producing a hymn of 6 stanzas of 6 lines It is to this arrangement of the text that most modern editors both in Great Britain and America are indebted for their centos. Portions of the hymn in centos of varying lengths, are in extensive use.
-- Excerpts from John Julian, Dictionary of Hymnology (1907)