Sayyiduna Jarir (may Allah be pleased with him) narrates: I came to the Prophet (peace and blessings be upon him) and said: "O Messenger of Allah! I will pledge allegiance to you upon emigration." The Prophet (peace and blessings be upon him) took my pledge and stipulated upon me that I must also act sincerely towards every Muslim, so I pledged allegiance to him upon this as well. (Allamah al-Haythami says:) I say: In the Sahih it is mentioned that the Prophet (peace and blessings be upon him) imposed upon me the condition that I must act sincerely towards every Muslim.
Al-Tabarani recorded it through various routes, the narrators of some of which are the narrators of the Sahih.
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب المناقب / 15999