Taraweeh prayers

The Prophet (pbuh) led his companions in prayer (Taraweeh) for several nights, and then on the third or fourth night he did not come out to them. When morning came He (pbuh) said: “Nothing prevented me from coming out to you except the fact that I feared that it would be made obligatory for you.”
[Sahih Al-Bukhari]

Commentary:
It is prescribed to offer the night prayers in Ramadan in congregation or individually, but it is better to do it in congregation than to do it individually. The Prophet (pbuh) led his companions in offering these prayers in congregation for several nights. It is proven in al-Sahihayn (Sahih al-Bukhari and Muslim) that the Prophet (pbuh) led his companions in prayer (Taraweeh) for several nights, and then on the third or fourth night he did not come out to them. When morning came He (pbuh) said: “Nothing prevented me from coming out to you except the fact that I feared that it would be made obligatory for you.” (Sahih Al-Bukhari)

According to the version narrated by Muslim He (pbuh) said: “But I feared that night prayers would be made obligatory for you and you would not be able to do them.”
Offering Taraweeh prayer in congregation is something that is established by the Sunnah of the Prophet (pbuh). The Prophet (pbuh) stated the reason why he did not persist in offering this prayer in congregation, which is that he feared that it might be made obligatory. This reason ceased to be applicable after the Prophet (pbuh) died, because when he (pbuh) died, the wahy (revelation) ceased and there was no longer any worry that it might be made obligatory.Once the reason, which was the fear of it being made obligatory, disappeared with the cessation of the wahy (revelation), then the fact that it is Sunnah to offer this prayer in congregation resumed.

After the death of the Prophet (pbuh), the Sahaabah (ra) prayed Taraweeh in small groups and individually, until ‘Umar (ra) united them behind a single imam.It was narrated that ‘Abd al-Rahmaan ibn ‘Abd al-Qaari’ said: I went out with ‘Umar ibn al-Khattaab (ra) one night in Ramadan to the masjid, and the people were scattered, with one man praying by himself and another with a group of men following his prayer. ‘Umar (ra) said: “I think that if I gather them behind one reader, it will be better.” Then he decided to unite them behind Ubayy ibn Ka’b (ra). Then I went out with him on another night, and the people were praying behind their reader. ‘Umar (ra) said: “What a good innovation this is. But the prayer that they forget about and sleep is better than the one they are offering.” (Sahih Al-Bukhari)

Shaykh al-Islam Ibn Taymiyah (may Allah have mercy on him) said in ‘Majmoo al-Fataawa’, when refuting the view of those who quoted ‘Umar’s words “What a good innovation this is” as meaning that innovation (bid’ah) is permissible:With regard to qiyaam (night prayers) in Ramadan, the Messenger of Allah (pbuh) introduced this to his ummah, and he led them in prayer for a number of nights, because at his time they used to pray in congregation and individually. But he did not persist in leading them in one congregation, lest that be made obligatory for them. When the Prophet (pbuh) died, sharee’ah was established (and would not change after that). When ‘Umar (ra) became caliph, he united them behind one imam, Ubayy ibn Ka’b, who united the people in one congregation on the orders of ‘Umar ibn al-Khattaab (ra). ‘Umar (ra) was one of the Rightly-Guided Caliphs, of whom the Prophet (pbuh) said: “I urge you to adhere to my Sunnah and the way of the Rightly-Guided Caliphs after me; cling tightly to it.” So what he did was Sunnah but he said, “What a good innovation this is,” because it was an innovation in the linguistic sense, as they were doing something that they had not done during the life of the Messenger of Allah (pbuh), i.e., gathering to do this, but it is Sunnah in the shar’i sense.”

It says in ‘al-Mawsoo’ah al-Fiqhiyyah’:“From the time of ‘Umar (ra), the Rightly-Guided Caliphs and the Muslims regularly offered Taraweeh prayer in congregation. ‘Umar (ra) is the one who united the people in offering the prayer behind a single imam.
Asad ibn ‘Amr ibn Abi Yoosuf (may Allah have mercy upon him) said: I asked Abu Haneefah (may Allah have mercy upon him) about Taraweeh and what ‘Umar (ra) did. He said: Taraweeh is a confirmed Sunnah, and ‘Umar (ra) did not base his decision on speculation and he was not introducing bid’ah (an innovation). He did not enjoin it except because of what he knew from the Messenger of Allah (pbuh). ‘Umar introduced this and gathered the people behind Ubayy ibn Ka’b (ra) and he offered this prayer in congregation, at the time when the Sahaabah – the Muhaajireen and Ansaar (ra) – were still alive, and no one among them objected to that, rather they helped him and agreed with him, and also enjoined it.”

And Allah knows best!