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." (FR)
English reference (FR): Vol. 1, Book 1, Hadith 516 (FR)
Arabic reference (FR): Book 1, Hadith 556 (FR)