The children of Israel were just freed from slavery in Egypt by God who demonstrated His great power to the Egyptians and Israel. They saw the plagues and the great sea open for them to pass and then drown the Egyptians as they pursued them. Now in the wilderness of sin they find themselves faced without bread and water. So they grumbled at Moses - it’s his fault.
A wilderness can be frightening. Oftentimes we find ourselves in a wilderness just like the children of Israel, and we have to make a choice. The children of Israel had to make a choice; they had three alternatives to choose from:
1. Return to the security of slavery in Egypt.
2. Camp in the wilderness of sin.
3. Move with haste to the Promised Land.