He should not cease (to pray) unless he hears a sound or perceives a smell (of passing wind).
Sunan Abi Dawud Book 1, Hadith 176
← Previous Hadith The Prophet (ﷺ) saw a person offering prayer, and on the back of his foot a small part equal to the space of a dirham remained unwashed; the water did not reach it. The Prophet (ﷺ) commanded him to repeat the ablution and prayer.

Sunan Abi Dawud Book 1, Hadith 175 Next Hadith → The Messenger of Allah (ﷺ) said: If any one of you offers prayer and feels a movement between his paddocks, but is doubtful whether or not his ablution broke, he should not cease praying unless he hears a sound or perceives a smell.

Sunan Abi Dawud Book 1, Hadith 177