The command to follow the imam in his actions

It is narrated from Sayyiduna Mu'awiyah bin Abi Sufyan (may Allah be pleased with them both) that the Messenger of Allah (peace and blessings be upon him) said: "When the imam prays sitting (due to an excuse), then all of you should also pray sitting (following him)."
The narrator said: (On hearing this hadith) the people were amazed at the truthfulness of Sayyiduna Mu'awiyah (may Allah be pleased with him) and at the accuracy of (the report he narrated).

It is narrated from Sayyiduna Abd al-Rahman bin Awf (may Allah be pleased with him) that when the Messenger of Allah (peace and blessings be upon him) came to Sayyiduna Abd al-Rahman bin Awf (may Allah be pleased with him) while he was leading the people in prayer, Abd al-Rahman (may Allah be pleased with him) wanted to step back (from the place of the imam), but the Prophet (peace and blessings be upon him) gestured to him: "Stay in your place." So he led the prayer, and the Messenger of Allah (peace and blessings be upon him) prayed behind Sayyiduna Abd al-Rahman bin Awf (may Allah be pleased with him).
Imam Abu Ya'la al-Mawsili recorded this hadith in his Musnad, and its basis is also found in Sahih Muslim. This incident took place during the expedition of Tabuk, and it is an authentic and remarkable example of the Prophet (peace and blessings be upon him) praying behind one of his Companions.

Ibrahim bin Ubayd bin Rifa'ah narrates from Sayyiduna Jabir bin Abdullah (may Allah be pleased with them both): I went to Sayyiduna Jabir bin Abdullah (may Allah be pleased with them both) and found him leading his companions in the Asr prayer while sitting, and they were also sitting. Ibrahim said: I kept watching him until he gave the salam, then I said to him: 'Ghafara Allahu lak' (May Allah forgive you) - you are a Companion of the Messenger of Allah (peace and blessings be upon him), and you lead them in prayer while sitting?
He replied: "I am ill, so I am praying sitting, and it was I who ordered them to sit as well, for I heard the Messenger of Allah (peace and blessings be upon him) saying: 'The imam is a shield (and a leader), so when he prays standing, you too should pray standing, and when he prays sitting, all of you should pray sitting.'"
The chain of this hadith contains Khalid bin Ilyas, who is matruk al-hadith (abandoned); however, praying sitting behind the imam is also mentioned in other authentic hadith.

Musa, the son of Sayyiduna Abdullah bin Yazid (may Allah be pleased with him), narrates from his father that he used to lead the people in prayer here (at the place mentioned), and some people would put their heads down in prostration before the imam prostrated, and would raise their heads before the imam raised his. So when he finished the prayer, he turned towards them and said: "O people! Why do you incur sin yourselves and also lead others into sin? I led you in prayer exactly like the prayer of the Messenger of Allah (peace and blessings be upon him), and I have not deviated from it (the Prophetic way (peace and blessings be upon him)) in the slightest."
Imam Abu Bakr bin Abi Shaybah recorded this hadith via al-Fadl bin Dukayn, Umar bin Musa and Musa bin Abdullah bin Yazid.

Sayyiduna Ali bin Shayban narrates from his father (may Allah be pleased with them both) that he said: I prayed behind the Prophet (peace and blessings be upon him), and (during the prayer) a man raised his head (from bowing or prostration) before the Prophet (peace and blessings be upon him). When he (peace and blessings be upon him) completed the prayer and turned, he said: "Whoever raises his head before the imam, or puts it down (in prostration) before him, there is no prayer for him."
Imam Musaddad narrated this report in his Musnad; it contains the warning that preceding the imam invalidates the prayer or negates its reward.

It is narrated from Sayyiduna Abu Hurayrah (may Allah be pleased with him) that he said: "Indeed, the one who raises and lowers his head (in bowing and prostration) before the imam, his forelock is in the hand of a devil."
The narrator said: Imam Sufyan bin Uyaynah sometimes narrated this report as marfu' (attributed to the Prophet) and sometimes did not narrate it as marfu'.
Also, Imam al-Bazzar recorded it through Abd al-Aziz bin Muhammad from Muhammad bin Amr, and he said: "To our knowledge, Malih did not narrate any hadith from Sayyiduna Abu Hurayrah (may Allah be pleased with him) other than this."

It is narrated from Sayyiduna Anas (may Allah be pleased with him) that he said: "When we raised our heads from bowing while praying behind the Prophet (peace and blessings be upon him), we would remain standing until we saw that the Prophet (peace and blessings be upon him) had gone into prostration and had placed his blessed face firmly on the ground; then we would prostrate after that."
And the hadith of Abd al-Aziz bin Rufay' from an elder of the Ansar (may Allah be pleased with him) will come later, if Allah Almighty wills, in the chapter on the description of the prayer.