Exodus 17:11

Moses held up his hand, with the rod of God in it. This gesture, though fervent prayer was doubtless joined with it, seems not to have been the gesture of praying, which is the lifting up of both hands, but of an ensign-bearer, or of one ready to smite his enemies. Howsoever this was only a sign whereby Moses strengthened his faith, and quickened his prayers, and heightened the courage of the soldiers below, and protested that he expected victory not from the skill and prowess of his army, but from the assistance of God. When he let down his hand, Amalek prevailed; God so dispensing his favour, that the honour of the day and victory might be wholly ascribed to the rod and power of God, not to Israel.