The sin of Moses and Aaron

Numbers 20:12 And the Lord said to Moses and Aaron, “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.” (ESV)

Note that the verses immediately preceding say this:
10 Then Moses and Aaron gathered the assembly together before the rock, and he said to them, “Hear now, you rebels: shall we bring water for you out of this rock?” 11 And Moses lifted up his hand and struck the rock with his staff twice, and water came out abundantly, and the congregation drank, and their livestock. (Numbers 20)

I am not clear as to what Moses and Aaron did that was unbelieving. I have heard others say that it was because Moses struck the rock twice. Perhaps it was because Moses and Aaron said "shall we," rather than indicating that God was the one who would bring out the water. Perhaps it was something else. But their sin was apparently a combination of unbelief and not honoring God as they should have. All too common in this day and time. All too common, I fear, in my own life. God help me.

As I understand it, unbelief and pride are the two common and fundamental sin problems. They were so in the time of Moses and Aaron, and in 2008.

I noticed this passage as a consequence of following the ESV on-line Bible reading for a day in March. Thanks for reading.