Assembled at Thy great command. W. B. Collyer. [Missions.] First published in his Hymns Partly Coll. and Partly Original, 1812, No. 945, in 6 stanzas of 4 lines, and entitled, "A Missionary Hymn for the Opening of the Service." It was repeated in later editions of the same collection, and also was adopted by several of the older compilers. It is rarely found in modern hymnals in Great Britain, but its use in America is extensive. Usually it is abbreviated to four or less stanzas.
-- John Julian, Dictionary of Hymnology (1907)