Exodus 17:11

Israel prevailed. The lifting up of the hands has generally been regarded by ancient Jewish scholars, by the church Fathers, by the Reformers, and by many modern commentators as the sign or attitude of prayer. Throughout Bible times the custom of lifting up one’s hands in prayer was observed by pious and earnest worshipers. A few commentators have regarded the posture of Moses, with his hands lifted up, as the attitude of a commander superintending and directing the battle, but this opinion must be rejected, since Moses did not function as commander in chief. He had transferred the command to Joshua (v. 9). He himself engaged in earnest prayer to God for help and victory (PP 299). The question has been raised as to why Moses did not continue to pray even when his hands were weary. Only those who have attempted to pray continuously for long periods of time know how difficult such a procedure is. Perhaps when Moses dropped his hands because of fatigue, he rested also from the mental concentration necessary to prayer. To impress upon Israel the importance of intercessory prayer, God permitted success and failure to alternate accordingly. At the same time God wished His people to learn that their success was to be found in cooperating with His chosen leaders.