Abu Hurairah (may Allah be pleased with him) reports that the Messenger of Allah (peace and blessings be upon him) said: "There is no (obligation of) ablution unless a sound is heard or a smell is perceived."
Whoever has caused confusion for a scholar who does not distinguish between the concise and detailed narration, making him think that ablution is only obligatory due to that event which has a sound or a smell.
Hadith Referenceصحيح ابن خزيمه / جماع أبواب الأحداث الموجبة للوضوء / 27