We see that many people today object to celebrating Laylat al-Bara`ah in the masjid by performing group prayers and du`a. What is the reason for this, given that many Tabi`een observed this night?
See the excellent answer ‘Muadh ibn Jabal and the Night of Mid-Sha’ban by Sidi Samer Dajani‘ at Seeker’s Hub. To summarize:
…in the first century of Islam, it was the people of Shām who were known to celebrate the the Night of Mid-Sha’ban. Those who taught them that the Night of Mid-Sha’ban was a special night, and taught them to do extra prayers in this night, were scholars from the generation of the Tabi’een, those who studied under the Companions of the Messenger of Allah (may Allah bless him and grant him peace).
Now the question is, why was it in particular the Tabi’een of Shām that taught this?
Because they took it from the great Companion Muadh ibn Jabal (may Allah be pleased with him) who used to teach in Damascus. The Companions of the Messenger of Allah (may Allah bless him and grant him peace) spread to different parts of the world, and took with them the teachings that they heard from the Messenger of Allah. Because of this, in the first century of Islam, different regions within the Muslim world had different practices and fiqh, based on the different Companions that they learned from.