Sayyiduna Abu Dharr (may Allah be pleased with him) narrates that I asked the Messenger of Allah (peace and blessings be upon him) about everything, to the extent that I even asked him about touching (arranging) pebbles during prayer. So the Messenger of Allah (peace and blessings be upon him) said: "Arrange them once, or leave them (let them remain as they are)."
Hadith Referenceصحيح ابن خزيمه / جماع أبواب الأفعال المكروهة فى الصلاة التى قد نهي عنها المصلي / 916