Sahih Muslim 237b
Sahih Muslim · Book 2: The Book of Purification · Odd numbers when rinsing the nose and cleaning oneself with pebbles (istijmar)
Hammam b. Munabbih reported:
حَدَّثَنِي مُحَمَّدُ بْنُ رَافِعٍ ، حَدَّثَنَا عَبْدُ الرَّزَّاقِ بْنُ هَمَّامٍ ، أَخْبَرَنَا مَعْمَرٌ ، عَنْ هَمَّامِ بْنِ مُنَبِّهٍ ، قَالَ هَذَا مَا حَدَّثَنَا أَبُو هُرَيْرَةَ ، عَنْ مُحَمَّدٍ، رَسُولِ اللَّهِ صلى الله عليه وسلم فَذَكَرَ أَحَادِيثَ مِنْهَا وَقَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " إِذَا تَوَضَّأَ أَحَدُكُمْ فَلْيَسْتَنْشِقْ بِمَنْخِرَيْهِ مِنَ الْمَاءِ ثُمَّ لْيَنْتَثِرْ " .
This is what Abu Huraira transmitted to us from Muhammad, the Messenger of Allah (ﷺ), and he mentioned a number of a hadith, of which this is one: that the Messenger of Allah (ﷺ) said: When anyone amongst you (performs ablution) he must snuff his nostrils with water and then clean them.