The Israelites travelled through a long route through a wilderness with little natural provision. So they grumbled.
God gave hree signs
1. The glory of God appeared
2. The quails in the evening.
3. The manna in the morning. This went on till they reached the promised land.

How much are we depending on God to provide for our needs?
Jesus said 'do not worry'. God is greater than any of our concerns and worries.