Numbers 20 records a crucial mistake in Moses’ saintly life. The huge throng of Israelites that Moses had led out of Egypt were camped in the wilderness, in a spot with no water.
God ordered Moses to speak to a large rock, which would miraculously pour forth water. But instead of speaking to the rock, Moses struck it with his staff.
It did pour out water, but God punished Moses for not following His instructions to the letter: After forty years of leading the people of Egypt to Canaan, Moses would not be allowed to enter Canaan himself.