Exodus 15-17

God answered Pharaoh's question of who he is with 10 plagues that devastated Egypt. Egypt should have understood that the God of Israel was more powerful than their deities. And Israel was witness to the question and God's answer. But once they were on their own in the wilderness they began to have questions about their God. When they ran out of water they wondered if their God had forgotten to plan for this. There was a rock nearby that provided the water they needed, showing that God knew what he was doing. Next they ran out of food. So Israel asked the same question; why did God bring them to this place without a plan to feed them? But God did have a plan to feed them. Through the quail and manna God gave them everything they needed for the journey he had planned.
Stuart