Sunan Ibn Majah, Book 1, Hadith 361 (In-Book) ⓘ

It was narrated from Abu Hurairah that: The Prophet said: "Whoever uses stones to clean himself, let him use an odd number of stones. Whoever does that has done well, and whoever does not, there is no harm in it. Whoever uses a tooth stick should spit out (whatever he removes) and whoever removes (the particle of food) by dislodging it with his tongue should swallow it. Whoever does that has done well, and whoever does not, tere is no harm in it. Whoever goes to the toilet should conceal himself, and if he cannot find anything except a pile of sand (behind which to conceal himself), then he should use that, for the Shaitan plays with the backside of the son of Adam. Whoever does that has done well, and whoever does not, there is no harm in it."

حَدَّثَنَا مُحَمَّدُ بْنُ بَشَّارٍ، حَدَّثَنَا عَبْدُ الْمَلِكِ بْنُ الصَّبَّاحِ، حَدَّثَنَا ثَوْرُ بْنُ يَزِيدَ، عَنْ حُصَيْنٍ الْحِمْيَرِيِّ، عَنْ أَبِي سَعِيدِ الْخَيْرِ، عَنْ أَبِي هُرَيْرَةَ، عَنِ النَّبِيِّ ـ صلى الله عليه وسلم ـ قَالَ ‏ "‏ مَنِ اسْتَجْمَرَ فَلْيُوتِرْ مَنْ فَعَلَ ذَلِكَ فَقَدْ أَحْسَنَ وَمَنْ لاَ فَلاَ حَرَجَ وَمَنْ تَخَلَّلَ فَلْيَلْفِظْ وَمَنْ لاَكَ فَلْيَبْتَلِعْ مَنْ فَعَلَ ذَلِكَ فَقَدْ أَحْسَنَ وَمَنْ لاَ فَلاَ حَرَجَ وَمَنْ أَتَى الْخَلاَءَ فَلْيَسْتَتِرْ فَإِنْ لَمْ يَجِدْ إِلاَّ كَثِيبًا مِنْ رَمْلٍ فَلْيَمْدُدْهُ عَلَيْهِ فَإِنَّ الشَّيْطَانَ يَلْعَبُ بِمَقَاعِدِ ابْنِ آدَمَ مَنْ فَعَلَ فَقَدْ أَحْسَنَ وَمَنْ لاَ فَلاَ حَرَجَ ‏" ‏ ‏.‏