مِشْكَاةُ الْمَصَابِيحِ
Mishkat al-Masabih 980
Prayer
What may not be done during Prayer and what is permitted - Section 1
وَعَنْ مُعَيْقِيبٍ عَنِ النَّبِيِّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ فِي الرَّجُلِ يُسَوِّي التُّرَابَ حَيْثُ يَسْجُدُ؟ قَالَ: «إِنْ كُنْتَ فَاعِلًا فَوَاحِدَةً»
Mu'aiqib quoted the Prohpet as saying about a man who smoothed the ground where he prostrated himself, “If you do it, do it only once.” (Bukhari and Muslim.)
Mishkat al-Masabih, 980مُتَّفق عَلَيْهِ (الألباني)