The World Federation One Stop Fiqh

Ruling 740

If someone does not know the rulings (masāʾil) of prayers and cannot perform prayers correctly without learning the rulings, or, if he does not know what to do about doubts that arise in prayers (shakkiyāt) and about acts that are inadvertently left out (sahwiyāt), and if he deems it probable that one of these issues will arise in his prayer and on account of not learning the rulings he will not perform an obligatory act or he will commit an unlawful act, then in these cases, he must delay his prayer from the start of its prescribed time in order to learn the rulings. However, if he begins to perform his prayer at the start of its prescribed time with the hope that he will perform it correctly, and if during the prayer a problem for which he does not know the rule does not arise, his prayer is valid. However, if a problem for which he does not know the rule arises, it is permitted for him to act according to the more probable of two possibilities [concerning what he thinks the correct ruling is] in the hope that his responsibility is fulfilled, and to complete the prayer. And after the prayer, he must find out about the ruling; if his prayer was invalid he must perform it again, and if it was valid it is not necessary for him to repeat it.