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
← Previous Hadith 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 Next Hadith → when one of you leads the people in prayer, he should be brief, for among them are the sick, the aged and the needy.

Sunan Abi Dawud Book 2, Hadith 405