Sayyiduna Abu Umamah (may Allah be pleased with him) says: I heard the Messenger of Allah (peace and blessings be upon him) say: "Whoever goes to his bed in a state of purity, remembering Allah until drowsiness overtakes him, then at whatever hour of the night he wakes and asks Allah for any good of this world and the Hereafter, Allah will surely grant it to him."
Hadith Referenceالمعجم الكبير للطبراني / باب الصاد / 7537