Musnad Abu Ya'la al-Mawsili 159:8

Abu Khaythama narrated to us, Sufyan narrated to us, from Abu al-Zinad, from al-A'raj, from Abu Hurayrah, from the Prophet (peace and blessings of Allah be upon him), who said: "When one of you performs ablution, let him put [water] into his nose, then let him blow it out."