Narrated Abu Huraira:

Ibn Shihab (a sub-narrator) said, “Allah’s Apostle died and the people continued observing that (i.e. Nawafil offered individually, not in congregation), and it remained as it was during the Caliphate of Abu Bakr and in the early days of ‘Umar’s Caliphate.” ‘Abdur Rahman bin ‘Abdul Qari said, “I went out in the company of ‘Umar bin Al-Khattab one night in Ramadan to the mosque and found the people praying in different groups. A man praying alone or a man praying with a little group behind him. So, ‘Umar said, ‘in my opinion I would better collect these (people) under the leadership of one Qari (Reciter) (i.e. let them pray in congregation!)’. So, he made up his mind to congregate them behind Ubai bin Ka’b. Then on another night I went again in his company and the people were praying behind their reciter. On that, ‘Umar remarked, ‘what an excellent Bid’a (i.e. innovation in religion) this is; but the prayer which they do not perform, but sleep at its time is better than the one they are offering.’ He meant the prayer in the last part of the night(Tahajjut).
Sahih Bukhari, Volume 3, Book 32, Number 227

That he was informed by ‘Aisha, “Allah’s Apostle went out in the middle of the night and prayed in the mosque and some men prayed behind him. In the morning, the people spoke about it and then a large number of them gathered and prayed behind him (on the second night). In the next morning the people again talked about it and on the third night the mosque was full with a large number of people. Allah’s Apostle came out and the people prayed behind him. On the fourth night the Mosque was overwhelmed with people and could not accommodate them, but the Prophet came out (only) for the morning prayer. When the morning prayer was finished he recited Tashah-hud and (addressing the people) said, “Amma ba’du, your presence was not hidden from me but I was afraid lest the night prayer (Qiyam) should be enjoined on you and you might not be able to carry it on.” So, Allah’s Apostle died and the situation remained like that (i.e. people prayed individually). “
Sahih Bukhari, Volume 3, Book 32, Number 229 :

Narrated by Zaid bin Thabit
Allah’s Apostle made a small room (with a palm leaf mat). Allah’s Apostle came out (of his house) and prayed in it. Some men came and joined him in his prayer. Then again the next night they came for the prayer, but Allah’s Apostle delayed and did not come out to them. So they raised their voices and knocked the door with small stones (to draw his attention). He came out to them in a state of anger, saying, “You are still insisting (on your deed, i.e. Tarawih prayer in the mosque) that I thought that this prayer (Tarawih) might become obligatory on you. So you people, offer this prayer at your homes, for the best prayer of a person is the one which he offers at home, except the compulsory (congregational) prayer.”
Sahih Bukhari, Volume 8, Book 73, Number 134 :