Church of Sant'Agnese in Agone, Rome
The ox on the right is Luke's symbol as writer of the Gospel of Luke. The book and quill pen refer to his authorship of that book along with the Acts of the Apostles. The putto on the right holds up a copy of the image of the Virgin and Child that Luke was believed to have painted.
This is one of a set of portraits of the evangelists. See also SS. Matthew, Mark, and John.
More of Saint Luke
Photographed at the church by Richard Stracke, shared under Attribution-NonCommercial-ShareAlike license.