بُلُوغُ الْمَرَامِ
Bulugh al-Maram 108
The Book of Purification
The Manners of Answering the Call of Nature
وَأَصْلُهُ فِي أَبِي دَاوُدَ, وَاَلتِّرْمِذِيّ وَصَحَّحَهُ اِبْنُ خُزَيْمَةَ مِنْ حَدِيثِ أَبِي هُرَيْرَةَ - رضى الله عنه - بِدُونِ ذِكْرِ اَلْحِجَارَة ِ [1] .
and its Asl (original source) is in Abu Da’ud and At-Tirmidhi and Ibn Khuzaima graded it Sahih (sound) through Abu Huraira (rad) without mentioning the “stones”.]
Bulugh al-Maram, 108