Caravaggio, Conversion of Saint Paul on the Road to Damascus, circa 1600-01.
This painting is in the Cerasi Chapel, within the Basilica of Santa Maria del Popolo, in Rome (near the Spanish Steps and the Villa Borghese). The piece shown here is one of two paintings that Caravaggio made for this particular chapel, the other being the Crucifixion of Saint Peter. The two Caravaggio paintings are on either side of the altar, while the altarpiece is the Assumption of Mary by Annibale Carracci.
Apparently, Caravaggio’s first version of the Conversion of Saint Paul was rejected by his patron. (This earlier version was purchased by another patron and is now housed Odescalchi Balbi Collection in Rome.) The second version is rather less cluttered than the first attempt, and moreover the second version more effectively displays Paul’s surprise and terror. Or maybe the key was getting rid of Paul’s beard.
Source: Wikimedia Commons.