This fresco, by Giotto di Bondone, is from the Life of Christ series at the Arena Chapel (Cappella Scrovegni) in Padua, Italy. Giotto created it between 1304-06.
In this scene (number 30 in the series), Jesus washes the feet of his disciples before they celebrate the Passover.
Click on the image to enlarge the view.
Image online, courtesy Wikimedia Commons.