Sayyiduna Jabir bin Abdullah (may Allah be pleased with them both) narrates: The Prophet (peace and blessings be upon him) said: "Written on the gate of Paradise is: There is no god but Allah; Muhammad (peace and blessings be upon him) is the Messenger of Allah; Ali is the brother of the Messenger of Allah. (This was decreed) two thousand years before creation was created."
Al-Tabarani recorded it in al-Mu'jam al-Awsat. Its chain contains Ash'ath, the paternal cousin of al-Hasan bin Salih, who is da'if (weak), and it also contains a narrator whom I do not know. The hadith about the brotherhood established between the Companions will come later, in the chapter on the virtues of a group of the Companions.
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب المناقب / 14656
Hadith Gradingمحدثین:إسنادہ صحیح
Hadith Takhrij«أخرجه المعجم الأوسط للطبراني برقم: 5494»