Hammam bin Munabbih heard Sayyiduna Abu Hurayrah (may Allah be pleased with him) say that the Messenger of Allah (peace and blessings be upon him) said: "The prayer of one who has lost his ablution is not accepted until he performs ablution." A man from Hadramawt asked: What is 'al-hadath' (loss of ablution)? Sayyiduna Abu Hurayrah (may Allah be pleased with him) said: "When wind is passed, with a sound or without a sound."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 569
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
It is narrated from Sayyiduna Abu Hurayrah (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "When one of you feels something in his stomach, or is in doubt whether something has come out of it or not, he should not leave the mosque until he hears a sound or perceives a smell."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 571