O Thou Eternal Victim slain. C. Wesley. [Passiontide.] Published in the Hymns on the Lord's Supper, 1745, No. 5, in 3 stanzas of 6 lines (Poetical Works, 1868-72, vol. iii. p. 219). It is found in its full and unaltered form in the Wesleyan Hymn Book and other collections, both old and new. In the Salisbury Hymn Book, 1857; the Sarum, 1868; the Society for Promoting Christian Knowledge Church Hymns, 1871, and others, it reads "O Thou before the world began." In addition this hymn has been entirely rewritten in two forms, the first by Dr. Kennedy in his Hymnologia Christiana, 1863, as, "O first in sorrow, first in pain" ; and the second by T. Darling, in his Hymns, 1887, as, "Christ Jesus, ere the world began." Of these Dr. Kennedy's is the finer of the two.
--John Julian, Dictionary of Hymnology (1907)