Sunan an-Nasa'i 43

Arabic

أَخْبَرَنَا إِسْحَاقُ بْنُ إِبْرَاَهِيمَ، قَالَ أَنْبَأَنَا جَرِيرٌ، عَنْ مَنْصُورٍ، عَنْ هِلاَلِ بْنِ يِسَافٍ، عَنْ سَلَمَةَ بْنِ قَيْسٍ، عَنْ رَسُولِ اللَّهِ صلى الله عليه وسلم قَالَ ‏ "‏ إِذَا اسْتَجْمَرْتَ فَأَوْتِرْ ‏"‏ ‏.‏

Translation

It was narrated from Salamah bin Qais that the Messenger of Allah (ﷺ) said:"When you clean yourselves (with stones, after defecating), use an odd number

Authenticity

Sahih · Abu Ghuddah

Reference