“The Messenger of Allah ﷺ said: ‘When anyone of you gets up to perform prayer, then indeed mercy is facing him, so he should not smooth the pebbles.’” (Using translation from Ibn Mājah 1027)
قَالَ رَسُولُ اللَّهِ ﷺ «إِذَا قَامَ أَحَدُكُمْ إِلَى الصَّلَاةِ فَإِنَّ الرَّحْمَةَ تُوَاجِهُهُ فَلَا يَمْسَحِ الْحَصَا»