This is a momentous chapter consisting of four events: the death of Miriam (20:1); the quarreling over a lack of water at Meribah of Kadesh, after which Moses and Aaron learn they shall not enter the promised land (20:2-13); the refusal by Edom to let Israel pass through their territory (20:14-21); and the death of Aaron (20:22-29). With the exception of the stand-off with Edom, all these events share a common theme: the passing of Israel's first generation of (national) leaders. Aaron and Miriam die, while Moses is informed that he too — specifically for failing to trust the Lord — "shall not bring this assembly into the land" (20:12). Moses's ministry will, of course, continue for the remainder of Numbers and Deuteronomy. It will include three memorable victories over King Sihon of the Amorites, King Og of Bashan, and the Midianite hoards. But in the end, this one lapse in Moses' faith — according to which he gave vent to his own anger and failed "to show (the Lord's holiness before the eyes of the Israelites" (v. 12) — cost him dearly, so that, although he would ascend Mt. Nebo and view the promised land, he would not enter it. Thus, the summation from the epistle applies, sadly, to Moses as well as to Aaron, Miriam, and all but two (Joshua and Caleb) of the generation that passed through the Red Sea: "So we see that they were unable to enter because of unbelief" (Hebrews 3:19).
This incident at Meribah of Kadesh is what lies behind the brief summary we have in Psalm 106:
"They [Israel] angered the LORD at the waters of Meribah, and it went ill with Moses on their account; for they made his spirit bitter, and he spoke words that were rash." (Ps 106:32-33)In Numbers 20, however, while the rash and bitter anger of Moses is clear enough, the Lord's decision seems to be rendered without a great display of emotion. Indeed, if the Lord was angry there, his anger was remarkably restrained,for he makes the water flow for the people after Moses struck the rock a second time (v. 11). We can only wonder how long was the ominous pause between the first and second strike, and what may have run through Moses' mind as he waited and wondered what would happen next.