كتاب الصلاة
2  
The Book of Prayer
Bulugh al-Maram 241
Narrated Abu Dhar (RA):
Allah's Messenger (ﷺ) said: "When one of you is praying he must not remove pebbles (from his face) for the mercy is facing him." [Reported by al-Khamsah with a Sahih (authentic) chain].
وَعَنْ أَبِي ذَرٍّ ‏- رضى الله عنه ‏- 1‏ قَالَ : قَالَ رَسُولُ اَللَّهِ ‏- صلى الله عليه وسلم ‏-{ إِذَا قَامَ أَحَدُكُمْ فِي اَلصَّلَاةِ فَلَا يَمْسَحِ اَلْحَصَى , فَإِنَّ اَلرَّحْمَةَ تُوَاجِهُهُ } رَوَاهُ اَلْخَمْسَةُ بِإِسْنَادٍ صَحِيحٍ 2
Reference : Bulugh al-Maram 241
In-book reference : Book 2, Hadith 241
English translation : Book 2, Hadith 239
Bulugh al-Maram 241
And Ahmad added to the above Hadith:
"(remove the pebbles) once or leave (them)."
وَزَادَ أَحْمَدُ : "وَاحِدَةً أَوْ دَعْ" 1
Reference : Bulugh al-Maram 241
In-book reference : Book 2, Hadith 241
Hadith Text
Reference