Musannaf Ibn Abi Shayba 3:1084

Ibn Numayr narrated to us, from Ubayd Allah, from Nafi’, from Ibn Umar, that when the Emigrants (Muhajirun) arrived from Mecca, they stayed beside Quba. Salim, the freed slave of Abu Hudhayfah, led them in prayer because he was the one among them who knew the most Quran. Among them were Abu Salamah ibn Abd al-Asad and Umar ibn al-Khattab.