It was narrated that 'Amr bin 'Ata' said:
"I saw Sa'ib bin Yazid sniffing his garment, and I said: 'Why (are you doing) that?' He said: 'I heard the Messenger of Allah say: "No ablution (is needed) unless there is an odor or a sound." (IT)
English reference (IT): Vol. 1, Book 1, Hadith 516 (IT)
Arabic reference (IT): Book 1, Hadith 556 (IT)