In Exodus, God commands Moses to strike a rock, and promises to make water flow in the desert for the people.
Behold, I will stand before you there on the rock at Horeb, and you shall strike the rock, and water shall come out of it, and the people will drink.” And Moses did so, in the sight of the elders of Israel. (Exodus 17:6 ESV)
Later on, God tells Moses to speak to a rock, promising to make water flow in the desert again. However, Moses strikes the rock again instead of speaking to it. Because of just this one thing, God tells Moses that he will no longer be permitted bring the people into the Promised Land.
“Take the staff, and assemble the congregation, you and Aaron your brother, and tell the rock before their eyes to yield its water. So you shall bring water out of the rock for them and give drink to the congregation and their cattle.” 9 And Moses took the staff from before the Lord, as he commanded him. 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. 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.” (Numbers 20:8-12 ESV, emphasis added)
Why was the punishment so harsh for what seems like a small infraction? Was there something greater or more symbolic going on here?