Abd al-Malik bin Umayr narrates: Once Imam al-Sha'bi was narrating the maghazi (that is, accounts of the military expeditions). Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) passed by there and heard him narrating about them, and he said: "He remembers this better than I do, although I took part in these battles with the Prophet (peace and blessings be upon him)."
Al-Tabarani recorded it, and its narrators are thiqat (trustworthy).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب المناقب / 16442