Unbelief does terrible things to people, like turn them into raving lunatics.
Don’t believe me? Look at what it did to the Israelites. They had been rescued by God from the hand of Egypt and were on the verge of entering the Promised Land. But when Israelite spies brought back reports of enemies on steroids, the Israelites had a total meltdown. They said:
Because the LORD hated us he has brought us out of the land of Egypt, to give us into the hand of the Amorites, to destroy us. (Deut. 1:27)
This is crazy talk. The Israelites were God’s chosen, beloved, precious people. He busted them out of Egypt, water-bombed Pharaoh and his army, led them through the wasteland, fed them with bread from heaven, and promised to bring them into a land of rest. God was good to Israel. God loved Israel.
But the sin of unbelief always leads to faulty thinking about God. In the face of the enemy, Israel’s faith in God evaporated. Suddenly they viewed God through the lens of unbelief, a lens which made God appear to be cold, unloving, and hateful. Israel failed to believe God’s promise, which led them to doubt and accuse God.