Silsilat al-Ahadith al-Sahihah

It is narrated from Sayyiduna Abu Hurairah (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "Whoever spends the night in a state of ablution, an angel spends the night in his lower garment. Whenever that person wakes up during any part of the night, the angel says: O Allah! Forgive Your such-and-such servant, for he spent the night in a state of ablution."