It is narrated from Sayyiduna Abdullah bin Zaid (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) said: A new ablution becomes obligatory only when you perceive a smell or hear a sound.
Hadith Referenceمسند احمد / مسند المدنيين رضي الله عنهم اجمعين / 16442
Hadith Gradingحکم دارالسلام:حديث صحيح، محمد بن أبى حفصة ضعيف لكنه توبع