Why did God have Moses keep his hands raised during battle?
The Israelites were just beginning a relationship with YHWH. They obviously didn't know if they could trust him (complaining about the desert, food, water, etc.). However, it was going to be imperative that the Israelites trusted YHWH when they entered the promised land.
By causing the Israelites to win the battle when Moses raised his arms and lose when he lowered them, YHWH was showing the Israelites that it was God's power, not their own, that was responsible for the victory. There could be no other explanation. The lesson is that if they trust him, YHWH will provide. But if they try to do it by their own power, they will fail.
Created about 2 years ago