Sayyiduna Abu Sa'id al-Khudri (may Allah be pleased with him) narrates: The Prophet (peace and blessings be upon him) said: "If Allah Almighty were to send a messenger after me, He would have sent Sayyiduna Umar bin al-Khattab (may Allah be pleased with him)."
Imam al-Tabarani recorded it in al-Mu'jam al-Awsat. Its chain contains a narrator, Abd al-Mun'im bin Bashir, who is da'if (weak).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب المناقب / 14434