The lively brushstrokes and convincing vivacity of the face of this elderly man suggest that it is a study made directly from life. It could almost be a finished portrait, but is a preparatory study, used for the head of St Ambrose in a grand altarpiece. Rubens often made detailed studies of individual figures for large compositions, in addition to sketches of the whole design. These could be used by the master or copied by assistants working on the final painting. The subject of the altarpiece is St Ambrose Refusing the Emperor Theodosius Admission to the Church of Milan (Kunsthistorisches Museum, Vienna).