Maestro del polittico della cappella medici
St. John the Baptist with Saints Zenobius and Reparata

First half of the 14th century
Museo dell'Opera del Duomo (Florence)

The saints are identified by inscriptions along the base of the frame. Saint Reparata was Florence's patron before it adopted John the Baptist. Zenobius was the city's bishop in the 4th century.

St. John the Baptist wears his usual camel-skin tunic under an outer mantle. The scroll in his right hand reads voc clamantis in deserto parate viam domini rectas facite semi[tas eius], "A voice of one crying in the wilderness: Prepare ye the way of the Lord, make straight his paths" (Luke 3:4b). The verse characterizes John's preaching by alluding to Isaiah 40:3.

Read more about images of St. John the Baptist.
Read more about images of St. Reparata.
Read more about images of St. Zenobius.

Source: this page at Wikimedia Commons.