(151) باب مَنْ لَمْ يَمْسَحْ جَبْهَتَهُ وَأَنْفَهُ حَتَّى صَلَّى
Narrated Abu Sa`id Al-Khudri:
I saw Allah's Messenger (ﷺ) prostrating in mud and water and saw the mark of mud on his forehead.
Reference: Sahih al-Bukhari 836
In-book reference: Book 10, Hadith 229
USC-MSA web (English) reference(deprecated numbering scheme): Vol. 1, Book 12, Hadith 798