While the Israelites battled Amalek, Moses climbed to the top of the hill above the battleground and raised his hands heavenward. The Sages explain that he thereby spurred the Israelites to direct their attention to God, and with His assistance, the children of Israel were victorious.

“It was when Moses raised his hand, Israel prevailed, and when he lowered his hand, Amalek prevailed” (Exodus 17:11). Do the hands of Moses wage the war or damage the war effort? The verse serves to tell you that as long as the Israelites were looking upward after seeing Moses’ raised hands, and subjected their hearts to their Father in Heaven, they would prevail, but if not, they would fall in battle. (Mishna Rosh HaShana 3:8)