They asked the Apostle (ﷺ) about the removal of (pebbles) in prayer, whereupon he said: If you do it, do it only once.
Sahih Muslim Book 5, Hadith 60
← Previous Hadith It you must do so, do it only once.

Sahih Muslim Book 5, Hadith 59 Next Hadith → The Messenger of Allah (ﷺ) saw spittle on the wall towards Qibla, and scratched it away and then turning to the people said: When any one of you prays, he must not spit in front of him, for Allah is in front of him when he is engaged in prayer.

Sahih Muslim Book 5, Hadith 61