Al-Anfal · 8:11

11. And remember O believers when Allah made you fall asleep on that occasion, giving you a feeling of safety and peace from the fear you had of your enemy. He sent down rain from the sky on you, to purify you, and to remove the evil suggestions of Satan from you and to make your hearts strong, so you would be patient when you met the enemy in battle. It also made your feet firm, by making the sandy ground hard so that your feet would not sink and slip on it.