Beshalach - Sh'vi'i
Along Came Amalek
The Jews moved their camp to Refidim where, again, there was no water. And, again, they complained to Moshe.
"What do you want from me?" he asked. "Are you trying to antagonize G-d?"
The people replied with their usual refrain of, "Why did you bring us out of Egypt, just so we could die of thirst in the desert?" (Mind you, lack of water is a legitimate complaint, but there's a right way and a wrong way to go about things.)
Moshe turned to G-d, Who told him to take his staff and strike a particular boulder in front of everyone. Moshe did this and water came gushing out. The place became known as Maasah U'Merivah ("test and strife") because of the way the people provoked G-d there.
And then, along came the nation of Amalek and started a war with Israel. Moshe had Yehoshua (Joshua) select men for battle. While Joshua and his forces fought, Moshe stood on an overlooking hill with his brother, Aharon, and his nephew Chur (son of Miriam). When Moshe raised his arms, it spurred the Jews on to victory, but when he lowered his arms, they lagged. Aharon and Chur sat Moshe on a rock and held his arms up, so Moshe was able to pray while Yehoshua led their armed forces to victory.
"Write this down," G-d told Moshe, "and tell Yehoshua, too, that I will wipe out any trace of Amalek." Moshe then built an altar to thank G-d for His eternal vigilance against that antagonistic nation.