Tabarra is Wajib (Obligatory)

عن جعفر بن محمد عليهما السلام :

وحب أولياء الله والولاية لهم واجبة، والبراءة من أعدائهم واجبة ومن الذين ظلموا آل محمد عليهم السلام وهتكوا حجابه فأخذوا من فاطمة عليها السلام فدك، ومنعوها ميراثها وغصبوها وزوجها حقوقهما، وهموا باحراق بيتها، وأسسوا الظلم وغيروا سنة رسول الله، والبراءة من الناكثين والقاسطين والمارقين واجبة، والبراءة من الأنصاب والأزلام: أئمة الضلال وقادة الجور كلهم أولهم وآخرهم واجبة، والبراءة من أشقى الأولين والآخرين شقيق عاقر ناقة ثمود قاتل أمير المؤمنين عليه السلام واجبة، و البراءة من جميع قتلة أهل البيت عليهم السلام واجبة

Narrated by Imam Jafar bin Mohammad (ع) as part of a long narration:

"And to love the friends (Awliya) of Allah is obligatory and (accepting) their Mastership (Wilayat) is obligatory. And disavow/staying away (Bara'at) from their enemies is obligatory and from those who oppressed Aal-e-Mohammad (ع) and tore their veil and took away Fadak from Fatima (ع) and deprived Her of Her inheritance and illegally snatched (Gasb) her rights and rights of Her Husband and intended/started to burn Her house and laid the foundation of oppression and changed the traditions (Sunnah) of the Prophet of Allah (ص)."

"And Bara'at from the Nakiseen (those who broked the pledge i.e. people who fought Imam Ali in the battle of Jamal), Qasiteen (the unjust - Muawiya & his supporters) & Mariqeen (apostates of Nahrawan) is obligatory. And Bara'at from Ansaab & Azlaam (these are 2 words used in Holy Quran 5:90 referred to as uncleanliness and actions of Satan), the leaders (Imams) of wrong path and leaders of injustice/oppression all of them is obligatory and Bara'at from the greatest criminal from the first-ones and the last-ones i.e. the one who struck the she-camel of Thamud & the killer of Amir al-Momineen (ع) is obligatory and Bara'at from all those who killed the AhlulBayt (ع) is obligatory."

[Source: al-Khisal, Shaikh Sadooq, Pg.607]