Why did the Israelites complain in the desert before Moses struck the rock?
The Israelites complained because they and their flocks had no water in the desert. The multitude and animals were without a supply, so they began to murmur and complain before Moses struck the rock as God commanded. Their complaint arose from the scarcity of water.
Les explains that the Israelites were out in the desert with a great multitude of people and all their flocks, and there was no water. That lack of water caused them to murmur and complain. In the account, God then instructed Moses to take the elders of Israel and his rod, the same rod used when the Nile was turned to blood, and to strike the rock at Horeb once. Water would come out of the rock so the people could drink, and Moses did so in the sight of the elders of Israel.