Numbers 18-20

In this section, it was very interesting.. The Israelites just had the earth open up and consume them, fire came down and struck others, and plague hit them, which you'd think would solve any complaining on their part. God gives Aaron, his sons, and his tribe of Levi responsibilities on protecting the tabernacle. Then, they are given specific instructions on become pure from their uncleanness and sins using water. Chapter 20 is what really caught my attention: the Israelites are seen complaining again for their need of water, God gives Moses and Aaron instructions, and Moses and Aaron did not follow His instructions.. As a result,
Clark's commentary points out how Moses and Aaron disobeyed God's command.

Clarke's Commentary on the Bible

Because ye believed me not - What was the offense for which Moses was excluded from the promised land? It appears to have consisted in some or all of the following particulars:

1. God had commanded him (Numbers 20:8) to take the rod in his hand, and go and Speak To The Rock, and it should give forth water. It seems Moses did not think speaking would be sufficient, therefore he smote the rock without any command so to do.

2. He did this twice, which certainly in this case indicated a great perturbation of spirit, and want of attention to the presence of God.

3. He permitted his spirit to be carried away by a sense of the people's disobedience, and thus, being provoked, he was led to speak unadvisedly with his lips: Hear now, ye Rebels, Numbers 20:10.

4. He did not acknowledge God in the miracle which was about to be wrought, but took the honor to himself and Aaron: "Must We fetch you water out of this rock?"

Thus it plainly appears that they did not properly believe in God, and did not honor him in the sight of the people; for in their presence they seem to express a doubt whether the thing could be possibly done. As Aaron appears to have been consenting in the above particulars, therefore he is also excluded from the promised land.

The sins of Moses and Aaron had real consequences. They were (A) not helping the people trust God, (B) behaved like it was their power, (C) Not entering the land promised, and (D) Aaron died as a result of their sin. They also couldn't pass through the land of Edom, so they had to turn around. Moses and Aaron were supposed to be the people's leaders! This passage is very powerful to me, because we have to be listening carefully to the voice of God and being OBEDIENT to what God has for us to do.