Talhah bin Musarrif said: Rabi' bin Khuthaym added these words to the tashahhud: "His blessings and His forgiveness." Thereupon Alqamah said: We will stop where our knowledge stops: "O Prophet, peace be upon you, and the mercy of Allah and His blessings."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 9891