Abu Dawud Book 2, Hadith Number 792.

Narated By Some Companions of the Prophet : AbuSalih reported on the authority of some Companions of the Prophet (PBUH): The Prophet (PBUH) said to a person: what do you say in prayer?

He replied: I first recite tashahhud (supplication recited in sitting position), and then I say: O Allah, I ask Thee for Paradise, and I seek refuge in Thee from Hell-Fire, but I do not understand your sound and the sound of Mu’adh (what you say or he says in prayer). The Prophet (PBUH) said: We too go around it (paradise and Hell-fire).