Mishkat al-Masabih

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.)

وَعَنْ مُعَيْقِيبٍ عَنِ النَّبِيِّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ فِي الرَّجُلِ يُسَوِّي التُّرَابَ حَيْثُ يَسْجُدُ؟ قَالَ: «إِنْ كُنْتَ فَاعِلًا فَوَاحِدَةً»