(177) باب فِي مَسْحِ الْحَصَى فِي الصَّلاَةِ
Mu'aiqib reported the Prophet (ﷺ) as saying ; Do not remove pebbles while you are praying; if you do it out of sheer necessity, do it only once to smooth the pebbles.
Reference: Sunan Abi Dawud 946
In-book reference: Book 2, Hadith 557
English translation: Book 2, Hadith 946