The turbah (in Farsi muhr), the ground, or the object on which the worshipper places his forehead in the prostrations of canonic prayers must be canonically pure (ṭāhir). If a canonically pure turbah is placed on a canonically impure carpet or if the side of the turbah on which the worshipper places his forehead is canonically pure while the other side is canonically impure, the validity of the canonic prayer is not harmed, provided that worshipper’s forehead remains unaffected by the canonic impurity in question.