Lord, in this Thy mercy's day. I. Williams. [Lent—A Metrical Litany.] This hymn is taken from "Image the Twentieth," a poem on "The Day of Days; or, the Great Manifestation," in 105 stanzas of 3 lines, which forms a part of his work, The Baptistery; or, The Way of Eternal Life, 1844. It was given with slight changes in the Cooke & Denton Hymnal, 1853, in 6 stanzas. It has been repeated in full or in part in numerous collections in Great Britain and America, and is a most suitable metrical Litany for Lent.
--John Julian, Dictionary of Hymnology (1907)