1117. If a person intentionally changes the sequence of the prayers, for example, if he recites the other surah before reciting Surah al-Hamd, or performs the two Sajdah before Ruku, his prayers are void.
1118. If a person forgets a rukn (elemental part) of the prayers, and performs the next rukn, like, before performing Ruku if he performs the two Sajdah, his prayers would become void, as a measure of precaution.
1119. If a person forgets a rukn, and performs an act after it which is not a rukn, like, if he recites tashahhud without performing the two Sajdah, he should perform the rukn and should recite again the part which he performed erroneously, earlier than the rukn.
1120. If a person forgets a thing which is not a rukn, and performs a rukn which comes after it, like, if he forgets Surah al-Hamd and begins performing Ruku, his prayers is in order.
1121. If a person forgets an act which is not a rukn, and performs the next act which too, is not a rukn, like, if he forgets Surah al-Hamd and recites the other Surah, he should perform what he has forgotten, and then recite again the thing which he mistakenly recited earlier.
1122. If a person performs the first Sajdah thinking that it is the second one, or performs the second one under the impression that it is the first Sajdah, his prayer is in order; his first Sajdah will be treated as the first one, and his second Sajdah will be treated as the second one.