Sunan Ibn Majah, Hadith 514 ⓘ
It was narrated that Abu Sa'eed Al-Khudri said: "The Prophet was asked about doubts (concerning ablution) during prayer. He said: 'he should not leave until he hears a sound or detects an odor.'"
حَدَّثَنَا أَبُو كُرَيْبٍ، حَدَّثَنَا الْمُحَارِبِيُّ، عَنْ مَعْمَرِ بْنِ رَاشِدٍ، عَنِ الزُّهْرِيِّ، أَنْبَأَنَا سَعِيدُ بْنُ الْمُسَيَّبِ، عَنْ أَبِي سَعِيدٍ الْخُدْرِيِّ، قَالَ سُئِلَ النَّبِيُّ ـ صلى الله عليه وسلم ـ عَنِ التَّشَبُّهِ فِي الصَّلاَةِ فَقَالَ " لاَ يَنْصَرِفْ حَتَّى يَسْمَعَ صَوْتًا أَوْ يَجِدَ رِيحًا " .
also referenced under: Book 1, Hadith 554 (In-Book) & Volume 1, Book 1, Hadith 514 (DarusSalam)