To test Abraham's faith, God ordered him to sacrifice his only child Isaac. Abraham bound Isaac, laid him on the altar, and drew his knife to kill him. At that moment, an angel appeared and held back Abraham's hand, saying, "Now I know you are a God-fearing man, as you have not withheld your only son from me." Giulio Romano captured the scene's drama through the energetic swoop of the angel that hovers over Abraham's head. Abraham peers up astonished, while Isaac cowers on the stone altar. The figures all have squat, stocky proportions, broad faces, and hair and beards composed of solid, horn-like locks and curls. Some scholars speculate that Raphael, Giulio's master, may have begun the drawing, allowing his student to finish it. The drawing was probably made in preparation for a print. The artist used a stylus to outline the scene at first, then fleshed out the composition more fully in red chalk. An existing engraving corresponds in size and detail to this work.