The World Federation One Stop Fiqh

Ruling 65

It suffices if the anus is completely purified once with stone, a clod of earth, or cloth. However, it is better to purify it three times by using three pieces; and if it does not become purified after three times, one must keep trying to purify it until it becomes completely purified. However, there is no problem if traces remain that are not normally removed except by washing.