Behold the Lamb of God, which taketh [away the sin of the world]. These words, inscribed in Latin on the scroll held by Saint John the Baptist, announce the coming of Christ. Standing against a gold background and enclosed in a Gothic trefoil frame, Saint John wears a hair shirt that represents his ascetic life of prayer and penance. Using carefully curved brushstrokes, Luca di Tommè described the woolly texture of Saint John's shirt and the unruly curliness of his hair and beard. Patterned punch marks form the decorative halo around the saint's head. The Old Testament prophets Elijah and David, who predicted the coming of the Messiah, occupy the upper corners of the frame. This panel was once part of an altarpiece, possibly for a church in Siena.