(a) Sayyidah Aishah (may Allah be pleased with her) says that the Messenger of Allah (peace and blessings be upon him) said: "When one of you loses his ablution during the prayer, let him hold his nose and leave."
(b) Hisham (may Allah have mercy on him) narrates in a mursal report: When one of you loses his ablution on Friday, let him put his hand over his nose and leave.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجمعة / 5850