John the Baptist is shown in his camel-skin garment and carrying a reed cross. He was a few months older than Jesus. The two are often shown as youths, prior to the moment when John baptised Jesus in the River Jordan.
The painting is a late work of Guido Reni. He had treated the subject once before in a larger full-length painting now in the church of the Gerolamini in Naples (about 1612).