Two thirds of the book that first put Charles Wesley's own hymns into print was not written by either Wesley brother. Hymns and Sacred Poems drew heavily on material John Wesley had already gathered and printed elsewhere, his own earlier Collection of Psalms and Hymns among the sources, plus verse borrowed from writers outside the family circle entirely, George Herbert's devotional poetry and a German Moravian hymnal both among them. John was the collection's primary compiler and editor, choosing what stayed in and what was cut, which is why the surviving evidence of the printing itself, Strahan's press, Hutton's shop, the sale at Mr. Bray's address in London in March 1739, sits more cleanly under his name than his brother's.
What made the book matter historically was the remaining third. Among the new verse the brothers themselves contributed sat Charles Wesley's And Can It Be That I Should Gain, written the year before under the heading Free Grace, the first hymn of his own to reach a printed page. He had composed it to mark his own conversion of May 1738, and its opening wonder at a savior who left his Father's throne above for one particular sinner became, across the centuries that followed, one of the most sung expressions of personal assurance in the English hymn tradition, still placed sixth in a 2013 BBC national survey of Britain's favorite hymns. A borrowed, composite hymnal turned out to be the vehicle for the one new voice inside it that would outlast every source it had leaned on.