Exodus 17:11-14

11As long as Moses held up his hands, Israel would win, but as soon as he put his hands down, the Amalekites would start to win.

12Eventually, Moses’ hands felt heavy. So Aaron and Hur took a rock, put it under him, and he sat on it. Aaron held up one hand, and Hur held up the other. His hands remained steady until sunset.

13So Joshua defeated the Amalekite army in battle.

14The Lord said to Moses, “Write this reminder on a scroll, and make sure that Joshua hears it, too: I will completely erase any memory of the Amalekites from the earth.”