Salam in the prayers

1114. While a person sits after reciting tashahhud in the last Rak'at, and his body is tranquil, it is Mustahab to say: Assalamu 'alayka ayyuhan Nabiyyu wa rahmatullahi wa barakatuh.
Then he should say: Assalamu Alaykum and as a recommended precaution add to it Wa Rahmatullahi Wa Barakatuh. Alternatively, he can say: Assalamu Alayna Wa Ala Ibadi llahis Salihin. But if he recites this Salam, then as per obligatory precaution, he must follow it up with saying: Assalamu Alaykum.

1115. If a person forgets the salam of prayers, and remembers when the form of namaz has not be disrupted, nor has he performed any act, which if done intentionally or forgetfully, invalidates the prayers (e.g. turning away from Qibla), he should recite the salam and his prayers will be valid.

1116. If a person forgets the salam of prayers, and remembers after the form of prayers has been disrupted, or after he has performed an act which if done intentionally or forgetfully, invalidates the prayers (e.g. turning away from Qibla), his prayers are in order.