Sayyiduna Muslim bin al-Harith al-Tamimi (may Allah be pleased with him) narrates: The Prophet (peace and blessings be upon him) had a letter written for him in which he instructed the rulers after him regarding him, and he (peace and blessings be upon him) had it sealed.
This narration was recorded by Imam Ahmad and Imam al-Tabarani, and the narrators of both are thiqat (trustworthy).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الأدب / 13175
Hadith Gradingمحدثین:إسنادہ صحیح
Hadith Takhrij«اخرجه الطبراني فى المعجم الكبير (434/19) اخرجه احمد فى المسند (234/4) ، أخرجه مسند أحمد برقم: 17593»