An inscription in gothic letters identifies the sitter and dates the work: “In the year 1438, I painted this effigy of Master Heinrich von Werl, Doctor of Cologne.” A Provincial of the Franciscan Order in that German city beginning in 1432, Werl was full Professor of Theology and quite a famous preacher. On a trip to Tournai, he was able to contact the painter and have himself portrayed inside a room, kneeling next to Saint John the Baptist.

Campin's painting shows a clear influence of Roger van der Weyden in the great slenderness, elegant expression and curved figure of Saint John. The van Eyck brothers are also clearly echoed here in the landscape visible through the window, and the use of a convex mirror that reflects two Franciscans and the Baptist.

This work is paired with Saint Barbara (P1514), as the two were the doors of a triptych whose central panel has been lost.