Soon after leaving bondage in Egypt, the Israelite people got thirsty and complained. God instructed Moses to strike the rock at Horeb to get water for the people, and Moses did. And there was water for everyone. (Exodus 17:6)
While traveling through the desert almost four decades later, the people were thirsty again, but God instructed Moses this time to speak to the rock. (Numbers 20:8) Moses and Aaron knew that God was going to bring water from a rock again, because He told them He would. And He told Moses his part. Out of what I think is frustration because of the complaining of the people, Moses said to them in verse 10, “Listen now, you rebels; shall we bring forth water for you out of this rock?” Then he struck the rock, twice, and water poured forth.
God said this was not treating Him as holy before the people. (Numbers 20:12) Maybe it was because Moses’ frustration with the people was showing instead of his faith in God. (And maybe his trust was lacking a little, too, at this point, also verse 12).
Earlier in Numbers (11:11-15), Moses showed his frustration to God in private. God did not get upset with him, but gave Moses the help he needed. (Numbers 11:16-17)
The frustration is real, but so is the faith in God (even though it lags at times). What the world needs to see is that we deal with frustration with faith.