It is narrated from Sayyiduna Ibn Umar (may Allah be pleased with them both) that Salim, the freed slave of Abu Hudhayfah (may Allah be pleased with him) used to lead in prayer the Muhajirun who had migrated to Madinah, among whom were Sayyiduna Umar (may Allah be pleased with him) and other Muhajirun, because he knew the most Qur'an of them all.
Hadith Referenceالمعجم الكبير للطبراني / باب السين / 6342