Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) narrates: The Prophet (peace and blessings be upon him) taught me to recite the tashahhud in the middle of the prayer and at its end. He says: When the Prophet (peace and blessings be upon him) sat on his left hip in the middle of the prayer and at the end of the prayer, he would recite: "All forms of physical, verbal and financial worship are exclusively for Allah Almighty. Peace be upon you, O Prophet, and the mercy of Allah Almighty and His blessings. Peace be upon us and upon all the righteous servants of Allah Almighty. I bear witness that there is no god but Allah Almighty, and I bear witness that Sayyiduna Muhammad (peace and blessings be upon him) is His servant and His Messenger." He says: Then, if he was in the middle of the prayer, he would stand up after reciting the tashahhud; and if he was at the end of the prayer, after the tashahhud he would make whatever supplication Allah willed, and then he would give the salam. (Allamah al-Haythami says:) I say:
This narration is recorded in the Sahih in a shorter form than this. Ahmad recorded it, and its narrators have been declared trustworthy.
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الصلاة / 2860