It is narrated from Sayyiduna Abu Hurayrah (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) said: "Ablution is (required) from the sound (of wind) or from its smell. (This narration is abridged.)"
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 570