Sayyiduna Abdullah bin Amr (may Allah be pleased with him) narrated: Sayyiduna Mu'awiyah (may Allah be pleased with him) used to write in the presence of the Prophet (peace and blessings be upon him) (or: for the Prophet (peace and blessings be upon him)).
Al-Tabarani recorded it, and its chain is hasan (good).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب المناقب / 15924