10th century
Fresco
Church of San Crisogono in Trastevere, Rome

This is the earliest image of Benedict that I have encountered.  It is in the 8th century church beneath the present Church of San Crisogono. The episode is narrated in Book 2 of the Dialogues of Gregory the Great (cached).

The boy's condition is denoted by spots on his skin and also by a label that the artist placed between his feet (see detail).

More of St. Benedict