The taslim releases one from the prayer

Sayyiduna Jabir bin Samurah (may Allah be pleased with him) narrates: When we prayed behind the Messenger of Allah (peace and blessings be upon him), we would say, pointing with the index finger: 'As-salamu 'alaykum, as-salamu 'alaykum' (Peace be upon you, peace be upon you). The Prophet (peace and blessings be upon him) said: "What is the matter with people that they raise their hands in the prayer as though they were the tails of restive horses? Is it not enough for you, or he said: for them, that one places his hand on his thigh and then gives salam to his brother on his right and on his left?"

It is narrated from Sayyiduna Jabir bin Samurah (may Allah be pleased with him): When we prayed behind the Messenger of Allah (peace and blessings be upon him), one of us would give salam to those on his right and left with his hand. When the Messenger of Allah (peace and blessings be upon him) finished the prayer, he said: "What is the matter with you that you gesture with the hand as though they were the tails of restive horses? It is enough for you only" or (he (peace and blessings be upon him) said) "Is it not enough for you that one does like this?" Then he (peace and blessings be upon him) pointed with his blessed finger and said: "Then he gives salam to his brother on his right and on his left."

(a) It is narrated from Sayyiduna Ali (may Allah be pleased with him) that he (peace and blessings be upon him) said: "The key to the prayer is purification (wudu), what makes things forbidden in it is the takbir, and what makes them lawful again is the salam."
(b) A narration on this from Sayyiduna Abu Sa'id al-Khudri (may Allah be pleased with him) has already passed.

Sayyiduna Ali (may Allah be pleased with him) says: When a person has sat in the prayer for the length of the tashahhud and then (after that) loses his ablution, his prayer is complete.
The Commander of the Faithful, Sayyiduna Ali bin Abi Talib (may Allah be pleased with him), would never go against the hadith of the Prophet (peace and blessings be upon him). Even if this narration were authentic, the proof would still be the narration that he or someone else transmitted from the Prophet (peace and blessings be upon him), against which the saying of no member of the Ummah can serve as proof. The second answer is that this narration itself is weak.

(a) It is narrated from Abu al-Ahwas that Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) said: The key to the prayer is the takbir, and its conclusion is the salam. When the imam has given the salam, then stand up if you wish.
(b) This authentic report from Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) indicates the soundness of our position.

(a) It is narrated from al-Qasim bin Mukhaymirah that Alqamah took hold of my hand and narrated to me that Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) had taken hold of his hand, and the Messenger of Allah (peace and blessings be upon him) had taken hold of the hand of Sayyiduna Abdullah (may Allah be pleased with him), and he (peace and blessings be upon him) taught him the tashahhud (recited) in the prayer and said: "Say: 'At-tahiyyatu lillahi wa-s-salawatu wa-t-tayyibat, as-salamu 'alayka ayyuha-n-nabiyyu wa rahmatullahi wa barakatuh, as-salamu 'alayna wa 'ala 'ibadillahi-s-salihin' (All worship by words, deeds and wealth is for Allah. Peace be upon you, O Prophet, and the mercy of Allah and His blessings. Peace be upon us and upon all the righteous servants of Allah)."
(b) Abu Khaythamah narrates that some of my companions added this to this hadith, through al-Hasan: 'Ashhadu an la ilaha illallahu wa ashhadu anna Muhammadan 'abduhu wa rasuluh' (I bear witness that there is no god but Allah, and I bear witness that Muhammad (peace and blessings be upon him) is the servant of Allah and His Messenger).
(c) Abu Khaythamah says that, in my memory, this too has reached me through al-Hasan regarding the remainder of this hadith: "When you have done this, or completed this, then indeed your prayer is complete. Now if you wish to stand, then stand, and if you wish to sit, then sit."
(d) Ahmad bin Yunus narrated this hadith from Zuhayr and held that part of this hadith had been erased from his book or had worn away.
A group narrated this hadith from Abu Khaythamah Zuhayr bin Mu'awiyah and inserted the end of the hadith into its beginning (idraj); Yahya bin Yahya indicated that part of the hadith had gone from Zuhayr's memory from al-Hasan bin al-Hurr. Shababah bin Sawwar narrated it from Zuhayr and separated the end of the hadith from its beginning, making it the words of Abdullah bin Mas'ud, as though he took it from him before it went from his memory or his book.

Al-Hasan bin al-Hurr also narrated a report with the same meaning as the hadith of Yahya bin Yahya; it is the same up to his words 'al-salihin', then he said: 'Ashhadu an la ilaha illallahu wa ashhadu anna Muhammadan 'abduhu wa rasuluh' (I bear witness that there is no god but Allah, and I bear witness that Muhammad (peace and blessings be upon him) is the servant of Allah and His Messenger).
Sayyiduna Abdullah (may Allah be pleased with him) says: "When you have recited this, you have completed the prayer that was obligatory upon you. (Now it is your choice:) if you wish to stand, then stand, and if you wish to sit, then sit."
Ali (may Allah have mercy on him) said: Shababah is thiqah (trustworthy); he separated the end of the hadith and made it the words of Ibn Mas'ud, and this is more correct than the narration of those who inserted its end into the words of the Prophet (peace and blessings be upon him), and Allah knows best. Abu Ali al-Husayn bin Ali al-Hafiz said: Zuhayr erred in his narration from al-Hasan bin al-Hurr and inserted into the words of the Prophet (peace and blessings be upon him) what is not from his words, namely his saying: 'When you have done this, you have completed your prayer'; this is only from Abdullah bin Mas'ud.

(a) A narration like the hadith of Yahya bin Yahya and Shababah is reported from al-Hasan bin al-Hurr through another chain.

(a) It is narrated from Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him): The Prophet (peace and blessings be upon him) taught me the tashahhud; then he mentioned the complete hadith.
(b) Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) says: When you have finished your prayer, then if you wish, remain seated there, and if you wish, give the salam.
(c) The Shaykh (may Allah have mercy on him) says: This phrase, 'fa-idha faraghta min salatik' (so when you have finished your prayer), if it is preserved, is closer to the narration that has reached us from Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) about completing the prayer with the salam, and also to what we shall soon narrate from the Prophet (peace and blessings be upon him) about the salam. It is as though his (may Allah be pleased with him) intent was to oppose the one who holds that it is not permissible for the follower to turn away, after finishing the prayer, before the imam turns away. And even if the first wording is established from the Prophet (peace and blessings be upon him), it will be understood that the Prophet's (peace and blessings be upon him) teaching of the tashahhud to Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) was at the early time when the tashahhud was first prescribed. Later the command to send blessings upon the Prophet (peace and blessings be upon him) came. The proof of this is the Companions' saying: 'Qad 'arafna al-salam' (We have come to know the salam), that is, we have come to know the way of the salam, now tell us how we should send blessings upon you. Then, after that, concluding the prayer with the salam was prescribed. The salam was prescribed either together with it or some time after it. And Allah knows best. And what confirms this is the following report.

(a) It is narrated from Ata' bin Abi Rabah (may Allah have mercy on him) that before the command of the salam was revealed, when the Messenger of Allah (peace and blessings be upon him) completed the tashahhud in the prayer, he would turn his blessed face towards the people.
(b) It is also reported from Ata' (may Allah have mercy on him) in another narration, in which it says: 'Wa dhalika qabla an yunzal al-taslim' (that is, this was before the command to give the salam was revealed).
(c) Although this narration is mursal, it is in agreement with the connected, musnad narrations about the salam.

It is narrated from Sayyiduna Abdullah bin Amr (may Allah be pleased with them both) that the Messenger of Allah (peace and blessings be upon him) said: "When the imam has completed the prayer and is sitting, and then loses his ablution before speaking, his prayer is complete, and those of his followers who had completed the prayer, their prayer is also complete."
This is not authentic. Abd al-Rahman bin Ziyad alone narrated it, and there is disagreement over its wording from him. Abd al-Rahman is not used as proof; Yahya al-Qattan and Abd al-Rahman bin Mahdi did not narrate from him because of his weakness, and Ahmad bin Hanbal, Yahya bin Ma'in and other huffaz criticised him.