O Lord, how happy should we be. J. Anstice. [Rest and Peace in Jesus.] First published in his posthumous Hymns, 1836, No. 44, in 5 stanzas of 6 lines. In 1841 it was included in the Child's Christian Year, and from thence has passed into numerous hymnbooks in all English-speaking countries. It was probably suggested by the words of the Psalmist, "Cast thy burden upon the Lord, and He shall sustain thee;" but in the Hymns there is nothing to indicate its origin, as it is printed there without title or heading of any kind. Usually the text is slightly altered, that in the Hymnal Companion, although claiming to be the original, being at fault in no less than four instances. This hymn is the best known and most widely used of Anstice's hymns.
--John Julian, Dictionary of Hymnology (1907)