It was narrated from 'Asim bin Laqit bin Sabrah that his father said:
"I said: 'O Messenger of Allah! Tell me about ablution.' He said: 'Perform ablution properly and sniff water up into your nostrils, thoroughly, unless you are fasting.'" (IT)
English reference (IT): Vol. 1, Book 1, Hadith 407 (IT)
Arabic reference (IT): Book 1, Hadith 441 (IT)