Sayyidah Aishah (may Allah be pleased with her) narrates that the Prophet (peace and blessings be upon him) said: "When one of you breaks his ablution during the prayer, let him gesture with his hand over his face (holding his nose) and leave." This hadith is sahih (authentic) on the condition of the two Shaykhs (Bukhari and Muslim), but they did not record it because some of the students of Hisham bin Urwah narrated it from him as a statement of the Companion (mawquf).