صحيح ابن خزيمه
Sahih Ibn Khuzaymah
جماع أبواب الصلاة على البسطChapters on Praying on Mats
(423) بَابُ الْأَمْرِ بِالِانْصِرَافِ مِنَ الصَّلَاةَ إِذَا أَحْدَثَ الْمُصَلِّي فِيهَاThe chapter on the command to leave the prayer if one becomes impure during it
Hadith Q1019
وَوَضْعِ الْيَدِ عَلَى الْأَنْفِ كَيْ يُتَوَهَّمَ النَّاسُ أَنَّهُ رَاعِفٌ لَا مُحْدِثٌ حَدَثًا مِنْ دُبُرٍ
And the statement about placing the hand on the nose so that other worshippers think that he has a nosebleed, not that wind has passed from him.
