Though in the nature thereof, that with which a purer metal is mixed, be not base; yet, it abases the purer metal. […] [T]hough silver be a precious metal, yet it abases gold. Grace, and peace, and faith, are precious parts of our treasure here; yet, if we mingle them, that is, compare them with the joys, and glory of heaven; […] we abase, and over-alloy these joys, and that glory.
1629 February 12, John Donne, “Sermon CXXXVI. A Lent Sermon Preached to the King, at Whitehall, February 12, 1629”, in Henry Alford, editor, The Works of John Donne, D.D., Dean of St. Paul’s, 1621–1631. […] In Six Volumes, volume V, London: John W[illiam] Parker, […], published 1839, page 450