The painting illustrates a passage in the Book of Exodus, chapter 17, which describes how Moses and his two companions watched the battle from the hill.

And Moses said unto Joshua, Choose us out men, and go out, fight with Amalek: tomorrow I will stand on the top of the hill with the rod of God in mine hand.

And Joshua discomfited Amalek and his people with the edge of the sword.Millais depicts the "going down of the sun", when the three patriarchs watch the final moments of the battle.

F. G. Stephens commented that the painting depicted the conflict between the unyielding and steadfast willpower of Moses, and the physical and emotional exhaustion of his companions.

The painting contrasts dramatically in style with the contemporary religious works of Millais's former companion, William Holman Hunt, such as The Shadow of Death,[2] on which Hunt was working at the same time; however, it has been suggested that both pictures may refer to typological prefigurations of the crucifixion in scenes in which raised, outstretched arms signify both physical suffering and triumph.