‘Uthman b. Abul ‘As said that the last command God’s messenger gave him was, “When you act as imam for people, make the prayer short." Muslim transmitted it.
In a version by him it says that God's messenger said to him,…
Ibn ‘Umar said: God's Messenger used to command us to be brief, and he would recite as-Saffat (Al-Qur’an; 37) when he was our imam.
Nasa’i transmitted it.