The prophet (ﷺ) said to a youth: My nephew, what do you do in prayer? He replied: I recited fatihat al-katab and I ask Allah for paradise and seek his refuge from hell-fire I do not understand well your sound and the sound of mu’adh. The prophet (ﷺ) said: I and Mu’adh go around both (paradise and Hell-fire), or he said something similar.
Sunan Abi Dawud Book 2, Hadith 403
← Previous Hadith AbuSalih reported on the authority of some Companions of the Prophet (ﷺ): The Prophet (ﷺ) 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 (ﷺ) said: We too go around it (paradise and Hell-fire).

Sunan Abi Dawud Book 2, Hadith 402 Next Hadith → When one of you leads the people in prayer, he should be brief, for among them are the weak, the sick, and the aged. But when one of you prays by himself, he may pray as long as he likes.

Sunan Abi Dawud Book 2, Hadith 404