Abu Sulaymān, Mālik ibn al-Huwayrith, (may Allah be pleased with him) reported: We came to the Messenger of Allah (may Allah's peace and blessings be upon him) when we were young and of about the same age. We stayed with him for twenty nights. The Messenger of Allah (may Allah's peace and blessings be upon him) was merciful and compassionate; so, he realized our longing for our families. He asked us about our families whom we had left behind and we told him about them. Thereupon, he said: "Go back to your families and stay with them. Teach them (religion) and command them (to adhere to it), perform so-and-so prayer at so-and-so time, and when prayer becomes due, let one of you call the Adhān and let the oldest among you lead you in prayer."
Another version by Al-Bukhāri has this addition: "Pray as you saw me pray.”
Abu Mas‘ūd al-Ansāri (may Allah be pleased with him) reported that the Messenger of Allah (may Allah's peace and blessings be upon him) said: “The one who is the most versed in Allah's Book should lead the people in prayer. If they are equally versed in reciting it, then the one who is the most knowledgeable about the Sunnah; and if they are equal regarding the Sunnah, then the earliest one to emigrate; if they emigrated at the same time, then the earliest one to embrace Islam. No man must lead another in prayer where the latter has authority, or sit in his place in his house without his permission.”
Anas ibn Mālik (may Allah be pleased with him) reported: I have never prayed behind an Imām who was more brief and more perfect in prayer than the Prophet (may Allah's peace and blessings be upon him).
Abu Mas‘ūd al-Ansāri (may Allah be pleased with him) reported: A man said: "O Messenger of Allah, I would almost fail to attend the prayer because so-and-so prolongs it when he leads us." I never saw the Prophet (may Allah's peace and blessings be upon him) more angry in giving admonition than he was on that day. He said: "O people, you cause aversion to others. Whoever leads people in prayer should make it brief, for among them are the sick, the weak, and those with needs to be fulfilled."
Abu Hurayrah (may Allah be pleased with him) reported that the Prophet (may Allah's peace and blessings be upon him) said: "If any of you leads the people in prayer, let him shorten it, because among them are the weak, the sick, and the busy (who have needs to fulfill). If any of you prays alone, then let him prolong (his prayer) as much as he wishes."
‘Ā'ishah (may Allah be pleased with her) reported that the Messenger of Allah (may Allah's peace and blessings be upon him) prayed in his house during his illness. He prayed while sitting and the people prayed behind him while standing. He pointed to them to sit down. When he had finished the prayer, he said: "Verily, the Imām is appointed in order to be followed. So when he bows, you should bow, and when he raises his head, you should do the same. And if he says: 'Allah hears the one who praises Him,' you should say: 'Our Lord, all praise is due to You.' And if the Imām prays while sitting, you all should pray while sitting as well."
‘Abdullāh ibn Yazīd al-Khatmi al-Ansāri (may Allah be pleased with him) reported: Al-Barā' - and he is not a liar - said to me: "When the Messenger of Allah (may Allah’s peace and blessings be upon him) said: ''Allah hears the one who praises Him,' none of us would bend his back until the Messenger of Allah (may Allah’s peace and blessings be upon him) had fallen in prostration. We would then fall in prostration right after him."
Abu Hurayrah (may Allah be pleased with him) reported that the Prophet (may Allah's peace and blessings be upon him) said: "Isn't he who raises his head before the Imām afraid that Allah may transform his head into that of a donkey or his shape into that of a donkey?"
Abu Hurayrah (may Allah be pleased with him) reported that the Messenger of Allah (may Allah's peace and blessings be upon him) said: "They lead you in prayers. If they do well, then you will be rewarded; but if they make mistakes, then you will receive reward and the mistake will be theirs.”
