Sahih Muslim
The Book of Purification (Kitab Al-Taharah)
Book Number: 002 / Hadith Number: 459
Hammam b. Munabbih reported: This is what Abu Huraira transmitted to us from Muhammad, the Messenger of Allah (may peace be upon him), and he mentioned a number of a hadith, of which this is one: that the Messenger of Allah (may peace be upon him) said: When anyone amongst you (performs ablution) he must snuff his nostrils with water and then clean them.