Please give me authentic hadith prooving that taraweyh are 20 rakath.

Until approximately two centuries ago there were no two answers to this question. Every person until this time unanimously agreed that it is TWENTY Rakaats. Around the twelfth century a group calling itself the Ahle Hadith emerged and began propagating the fallacy that Taraweeh is only eight Rakaats. Recently, a small group in our country, in order to cast aside the following one of the four Madhabs, have begun blindly following the so called Ahle Hadith. Hence not only do they deprive themselves from the rewards of the entire twenty Rakaats, they also mislead other simpleminded people who are unaware of the facts and deprive them as well. At the same time those of weak Imaan who find the twenty Rakaats difficult due to their laziness and lack of realisation of the tremendous rewards of Taraweeh, have found a scapegoat in the baseless propaganda of the Ahle Hadith and its followers. The reality, however, is that twenty Rakaats of Taraweeh is Sunnatul Mua’kkadah (a greatly stressed Sunnah, deliberate omission of which is a sin).

ALL UNANIMOUS

In the time of Rasulullah (Sallallaahu Álayhi Wasallam) the Taraweeh Salaat was performed individually and in small groups. Rasulullah (Sallallaahu Álayhi Wasallam) stressed its performance but did not perform it with the congregation since he feared that it may then become  fardh (compulsory) upon the Ummah. In one narration, it is nevertheless mentioned that Rasulullah (Sallallaahu Álayhi Wasallam) performed twenty Rakaats of Taraweeh and the Witr in Ramadhaan. (Musannad ibn Abi Shaiba and Bayhaqi). This practice of performing the Taraweeh individually and in small groups continued in the time of Sayyidina Abu Bakr (Radhiallaahu Ánhu) and the initial years of the Khilafa of Sayyidina Úmar (Radhiallaahu Ánhu). Thereafter Hadhrat Úmar (Radhiallaahu Ánhu) appointed Ubayy ibn Kaáb (Radhiallaahu Ánhu) as the Imaam and gathered everybody in one Jama’ah behind him for the full twenty Rakaats of Taraweeh. At that time there were numerous Sahaabah (Radhiallaahu Ánhum) present. All of them agreed on this decision of Hadhrat Úmar (Radhiallaahu Ánhu). If this decision was contrary to Deen, the Sahaabah (Radhiallaahu Ánhu) would have never been tolerated it. Their consensus on this manner is itself a Shaée proof of twenty Rakaats being Sunnah. A number of narrations mention the performance of twenty Rakaats by the Sahaaba (Radhiallaahu Ánhum). Therefore, we find that the four great Imaams of the four Maddhabs, despite a number of minor differences among them on the interpretation and application of various aspects, are unanimous that Taraweeh is twenty Rakaats. This is authentically recorded in their books.

HARAMAYN

The aspect of Taraweeh is really as clear as daylight. Therefore, one will find that in the Haramayn of Makkatul Mukarramah and Madinah Munawwarah up to this day, from the very time of Umar (Radhiallaahu Ánhu), twenty Rakaats is performed in Jamaa. The Sahaaba (Radhiallaahu Ánhu), the Taabiéen (those who came after the Sahaaba (Radhiallaahu Ánhum), the Imaams of Fiqh (jurisprudence) and the entire Ummah, with the exception of the so called Ahle Hadith of recent times, has been unanimous on twenty Rakaats.

YOUR DECISION

Finally, in one Hadith Rasulullah (Sallallaahu Álayhi Wasallam) is reported to have said, ‘After me there will be much differences. Hence hold on to my Sunnah and the Sunnah of my rightly guided Khulafaa’. (Mishkãt). Twenty Rakaats of Taraweeh with Jamaa was the Sunnah of the rightly guided Khulafaa. In this latter day difference, who will you follow? The Sunnah of the Khulafaa of Rasulullah (Sallallaahu Álayhi Wasallam) or the way of those who contradict them??? You make the decision.

The administration of your masjid should consider the convenience of the people coming for tarawih. If there is another musjid nearby performing twenty rakaats taraweeh in a shorter space of time you may go there.

and Allah Ta’ala Knows Best

Mufti Ebrahim Desai