Musannaf Ibn Abi Shaybah 38536 — the first to do a thing, and who did

Sayyiduna al-Bara' (may Allah be pleased with him) said: The first of the Companions of the Messenger of Allah (peace and blessings be upon him) to come to us (in Madinah) were Sayyiduna Mus'ab bin Umayr and Sayyiduna Ibn Umm Maktum (may Allah be pleased with them both). The two of them began teaching the people the Qur'an. Then came Sayyiduna Ammar, Sayyiduna Bilal and Sayyiduna Sa'd. Then Sayyiduna Umar bin al-Khattab came with twenty people. Then the Messenger of Allah (peace and blessings be upon him) came. I have not seen the people of Madinah as happy about anything as I saw them at the arrival of the Prophet (peace and blessings be upon him).