When Allah cast sleep upon you as a security from Him for you from the fear of your enemy that they might overcome you, and He sent down upon you from the clouds pure water, to purify you by it from the outward ritual impurities, and to remove from you in the inward the whisperings of Satan and his thoughts, and to strengthen your hearts with patience at the fighting, and to firm thereby the feet of the believers by making the sandy ground firm with the rain so that the feet do not slip therein.