The World Federation One Stop Fiqh

Ruling 1017

If at the time of saying the obligatory dhikr of rukūʿ one’s body moves inadvertently or unintentionally to the extent that it is no longer still, it is better that after his body has become still once more, he says the dhikr again. However, there is no problem if his body moves a little such that it does not stop becoming still, or if he moves his fingers.