"Wherever G-d's name is being profaned, as when the Jewish People suffer blows and affliction, we must beseech G-d to prevent that profanation from occurring. Moses, in holding his hands up towards Heaven, was hinting to Israel that the entire focus on their war was on preventing G-d's name from being profaned. If Israel were victorious, G-d's name would be sanctified in the world, but if Israel were smitten and slain, G-d's name would be profaned. Therefore, Moses steadfastly kept his arms up, even though this was hard for him and he needed the help of Aaron and Chur. Moses persevered by dint of his belief that Israel's entire purpose in this world is to sanctify G-d's name, and that if they fulfill that purpose, then G-d will help them to achieve victory in their war."

Rav Yosef Dov Begun