Musnad Ahmad 30:1501

Hassan narrated to us, Ibn Lahi'ah narrated to us, Ibn al-Had narrated to us, from Muhammad ibn Ibrahim, from Isa ibn Talhah ibn Ubayd Allah, from Abu Hurairah, that the Messenger of Allah (peace and blessings of Allah be upon him) said: "When one of you performs ablution, let him blow water out from his nose (istinthar), for the devil spends the night upon his nostrils."