Just as God made an example out of Nadab, He also made an example of Moses, the mediator of God’s covenant with Israel. The people needed water in the Desert of Zin. God told Moses and Aaron how to get fresh water by speaking to the rock. Instead Moses struck the rock. Water flowed freely, but God was angry that His instruction had not been followed. This incident kept Moses and Aaron out of the Promised Land (Deuteronomy 1:37). God explained,
Because you did not believe in Me, to uphold Me as holy in the eyes of the people of Israel, therefore you shall not bring this assembly into the land that I have given them (Numbers 20:12).
God said that Moses did not believe in Him.
In what sense did Moses and Aaron “not believe” in the LORD? By this time in their lives, Moses and Aaron knew God well. They had often seen His power. He had often worked through their faith. Indeed, Moses would not have stood in full view of the Israelites and struck the rock, if he had not expected (believed) that water would flow forth. So, God used “believe” to mean more than expectation, or even assurance. God meant, “You did not believe in Me enough to honor Me as holy [by following My way, not yours].” Numbers 20 confirms this:
And the LORD said to Moses and Aaron at Mount Hor, on the border of the land of Edom, “Let Aaron be gathered to his people, for he shall not enter the land that I have given to the people of Israel, because you rebelled against My command at the waters of Meribah” (Numbers 20:23-24).
In Numbers 20:12 the sin is “You did not believe in Me.” In Numbers 20:24 the sin is, “you rebelled against My command.” In this sense, to disobey is to disbelieve. The believing person is the obedient person. Scripture has no difficulty speaking in these ways (Psalms 26:1-3; 78:5-56; 84:11-12; 86:1-2; 119:66-67; Zephaniah 3:2; John 3:36).