Sayyiduna Abdullah bin Buhaynah (may Allah be pleased with him) narrates that the Messenger of Allah (peace and blessings be upon him) led us in two rak'ahs of one of the prayers, then he (peace and blessings be upon him) stood up without sitting (he did not recite the tashahhud), and the worshippers stood up along with him (peace and blessings be upon him). When he (peace and blessings be upon him) had completed the prayer, and we were waiting for him to give the salam, he (peace and blessings be upon him) said the takbir and performed two prostrations while sitting before giving the salam, then gave the salam.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3846
Sayyiduna Ibn Buhaynah (may Allah be pleased with him) narrates that the Messenger of Allah (peace and blessings be upon him) stood up after two rak'ahs of the Zuhr prayer and did not sit in them (for the tashahhud). When he (peace and blessings be upon him) had completed his prayer, he performed two prostrations, and after that he gave the salam.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3847
Sayyiduna Abdullah bin Malik (may Allah be pleased with him) narrates that the Messenger of Allah (peace and blessings be upon him) forgetfully stood up after two rak'ahs without the sitting, and continued his prayer. When he was near the end of his prayer, he performed two prostrations before giving the salam, then gave the salam.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3848
Amir (may Allah have mercy on him) narrates that Sayyiduna al-Mughirah bin Shu'bah (may Allah be pleased with him) led us in prayer and stood straight up after two rak'ahs without sitting. The people said 'Subhan Allah' (Glory be to Allah), but he did not sit. Then, when he gave the salam, he performed the two prostrations of forgetfulness, and then said: "I saw the Prophet (peace and blessings be upon him) doing it this way."
Regarding prostrating before the salam, the hadith of Sayyiduna Abdullah bin Buhaynah (may Allah be pleased with him) is more authentic than this. And Allah knows best.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3849
(a) Qays bin Abi Hazim (may Allah have mercy on him) narrates: Sayyiduna Sa'd bin Abi Waqqas (may Allah be pleased with him) led us in prayer, and after two rak'ahs he immediately stood straight up. The people began saying Subhan Allah, but he continued his prayer. Then, after giving the salam, he said: I did just as I saw the Messenger of Allah (peace and blessings be upon him) do.
(b) This narration was reported by Yahya bin Yahya (may Allah have mercy on him) from Abu Mu'awiyah (may Allah have mercy on him), and he added in it: He performed the two prostrations of forgetfulness when he finished the prayer with the salam.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3850
This narration with the same meaning is also reported through another chain.
Bayan narrated it from Qays and made it mawquf (stopping) at Sayyiduna Sa'd (may Allah be pleased with him).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3851
Abd al-Rahman bin Shimasah (may Allah have mercy on him) narrates: Sayyiduna Uqbah bin Amir al-Juhani (may Allah be pleased with him) led us in prayer. He was supposed to sit, but he stood up. The people said: 'Subhan Allah', 'Subhan Allah' (Glory be to Allah)! But he did not sit and remained standing. When he was at the end of the prayer, he performed the two prostrations of forgetfulness while sitting. When he gave the salam, he said: "I heard you just now saying Subhan Allah so that I would sit, but the Sunnah is what I did."
This has been narrated from a large number of the Companions, and what we have mentioned is sufficient. Wa billahi al-tawfiq (and success is only through Allah).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3852