What did Aaron do wrong at the Mei Merivah?

(1) The Israelites arrived in a body at the wilderness of Zin on the first new moon, and the people stayed at Kadesh. Miriam died there and was buried there. (2) The community was without water, and they joined against Moses and Aaron. (3) The people quarreled with Moses, saying, “If only we had perished when our brothers perished at the instance of the LORD! (4) Why have you brought the LORD’s congregation into this wilderness for us and our beasts to die there? (5) Why did you make us leave Egypt to bring us to this wretched place, a place with no grain or figs or vines or pomegranates? There is not even water to drink!” (6) Moses and Aaron came away from the congregation to the entrance of the Tent of Meeting, and fell on their faces. The Presence of the LORD appeared to them, (7) and the LORD spoke to Moses, saying, (8) “You and your brother Aaron take the rod and assemble the community, and before their very eyes order the rock to yield its water. Thus you shall produce water for them from the rock and provide drink for the congregation and their beasts.” (9) Moses took the rod from before the LORD, as He had commanded him. (10) Moses and Aaron assembled the congregation in front of the rock; and he said to them, “Listen, you rebels, shall we get water for you out of this rock?” (11) And Moses raised his hand and struck the rock twice with his rod. Out came copious water, and the community and their beasts drank. (12) But the LORD said to Moses and Aaron, “Because you did not trust Me enough to affirm My sanctity in the sight of the Israelite people, therefore you shall not lead this congregation into the land that I have given them.” (13) Those are the Waters of Meribah—meaning that the Israelites quarrelled with the LORD—through which He affirmed His sanctity.

(8) תריבהו וגו׳ THOU DIDST STRIVE WITH HIM [AT THE WATERS OF MERIBAH]... Thou didst seek an occasion against him to come with a pretext, for if Moses said, “Hear now, ye rebels”, what sin did Aaron and Miriam commit? (why were they not allowed to enter the land?).

(8) ודברתם אל הסלע, God did not command Moses to take the staff in order to strike the rock as he had commanded him in Exodus 17:6. He only commanded Moses to display the staff to remind them that they had again been very obstinate. They had acquired this attribute in Numbers 17:25 when the Torah speaks of למשמרת לאות לבני מרי, “to be kept as a lesson to rebels.” However, the water was to be produced merely by speaking to the rock.