مسائل المنتخبه (Articles Of Islamic Acts) - الخوئي، السيد أبوالقاسم - الصفحة ٢٧٧ - ADDITION AND OMISSION OF THE ACTS AND CONDITIONS OF PRAYERS
the prayers, invalidates the prayers (for example, if he has turned his
back towards Qibla) his prayers is invalid. In case. however, he has not
performed intentionally or by mistake an act, which invalidates the
prayers, he should perform immediately that part of the prayers which he
forgot to perform and should offer two sajdatus sahu for unnecessary
salaam.
١٢٧٩. If a person performs after the salaam of
prayers an act which invalidates the prayers, if done during the prayers
(for example if he turns his back towardsQibla) and recollects later
that he has not performed the two last prostrations, his prayers is
invalid. And if he recollects this before he performs any act
whichinvalidates the prayers, he should perform the two prostrations
which he forgot to perform and should recite tashahhud again, and recite
salaam of the prayers and shouldperform the two sajdatus sahv for the
salaam already uttered by him.
١٢٨٠. If a person realizes that he has offered
the prayers before its time set in, or offered it with his back facing
Qibla he should offer that prayers again, andif the prescribed time for
it has passed he should perform its qaza. In case, however, he realizes
that he has offered the prayers being the right or left side of Qibla
andthe time for prayers has not yet passed, he should offer it again.
And if the time of prayers has passed, it is not unlikely that the qaza
prayers need not be offered exceptwhen this act is due to the person not
knowing the orders on the subject.