“Abu Ja‘far (a.s.), has said, ‘While taking Wudu’ if you are not certain of washing your forearm, you must go back to wash it and repeat all of the acts of Wudu’ that you doubt about its being washed or wiped which Allah has commanded to be done. This applies when you are still taking Wudu’, but when you complete Wudu’, stand up and move to another condition such as Salah (prayer) or something else, and then doubt about something which Allah, most High has mentioned or has made obligatory on you as part of Wudu’, then there is nothing necessary for you to do. If during Wudu’ you doubt about wiping your head and you can find moisture in your beard, you must use such moisture to wipe your head and feet and if you do not find such moisture, you must not consider your Wudu’ invalid because of such doubt but you must proceed to your Salah (prayer). If you become certain that your Wudu’ is left incomplete, you must return to complete that which you are certain is left incomplete.’ Hammad has said that Hariz said that Zurarah has said, ‘I asked him (the Imam) about a man who has left out a certain part of his forearm or a certain part of his body for Ghusl (bath) because of sexual relation.’ He (the Imam) said, ‘If one doubts so and there is still moisture on him when he is in his Salah (prayer), he must wipe that part. If he becomes certain of a part being left incomplete, he must go back to complete it by pouring water on the part which is left dry and is without moisture. If one doubts while he has already assumed another condition, he must proceed to his Salah (prayer). There is nothing necessary for him to do about it. However, if it is discovered to have been left incomplete, he must go back to pour water on it; but if he finds moisture on it he only must wipe it and perform his Salah (prayer) again with certainty. If he has doubt about it there is nothing necessary for him to do because of such doubt and he must proceed to his Salah (prayer).”’