Muwatta Malik, Book 2, Hadith 3 (USC-MSA)

Yahya related to me from Ibn Shihab from Abu Idris al-Khawlani from Abu Hurayra that the Messenger of Allah, may Allah bless him and grant him peace, said, "The person doing wudu should snuff water up his nose and blow it out again."

وَحَدَّثَنِي عَنْ مَالِكٍ، عَنِ ابْنِ شِهَابٍ، عَنْ أَبِي إِدْرِيسَ الْخَوْلاَنِيِّ، عَنْ أَبِي هُرَيْرَةَ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ ‏ "‏ مَنْ تَوَضَّأَ فَلْيَسْتَنْثِرْ وَمَنِ اسْتَجْمَرَ فَلْيُوتِرْ ‏" ‏ ‏.‏

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also referenced under: Book 2, Hadith 35 (In-Book)