Are the tarawih prayers from the Sunnah of 'Umar or from the Sunnah of the Prophet?

Question : Here we ask: Are they from the Sunnah of 'Umar or from the Sunnah of the Prophet (peace and blessings be upon him)? Some people have claimed that they are from the Sunnah of 'Umar, citing as evidence that 'Umar ibn al-Khattab ordered Ubayy ibn Ka'b and Tamim al-Dari to lead the people in eleven rak'ahs. He went out one night while the people were praying and said, "What a good religious innovation (bid'ah) this is." This indicates that there was no prior prescription for it, and thus it would be from the Sunnah of 'Umar, not from the Sunnah of the Prophet (peace and blessings be upon him).

Answer : In that case, we may counter this by saying that it is not a Sunnah, because its cause existed during the time of the Messenger (peace and blessings be upon him), yet he did not do it.
The rule is that if the cause for something existed during the time of the Prophet (peace and blessings be upon him) and he did not do it, then it is not a Sunnah, because how would the Messenger leave it alone while the cause is present? What is the cause here? Ramadan existed during the time of the Prophet (peace and blessings be upon him), so since he did not do it, it was not a Sunnah. On this basis, if you pray the obligatory prayer in Ramadan, go to your house and pray, and do not pray with the people, do you understand? But this is a weak opinion, and its proponent overlooked what is established in the two Sahihs and others, that the Prophet (peace and blessings be upon him) stayed away, he stayed away and did not pray, and said, "I was afraid that it would become obligatory upon you." So the tarawih prayers were established by what? By the Sunnah of the Prophet (peace and blessings be upon him). The Prophet (peace and blessings be upon him) mentioned the obstacle to continuing with them, not the obstacle to their prescription, which was the fear that they would become obligatory. This fear was removed by the death of the Messenger (peace and blessings be upon him); it was removed, because when the Prophet (peace and blessings be upon him) died, revelation ceased, so there was safety from it becoming obligatory. When the cause is removed, the effect must be removed. When the cause, which was the fear of it becoming obligatory due to the descent of revelation, is removed, what happens? The effect is removed, or the removal of the effect is established. And thus it returns to being a Sunnah.