Musnad Ahmad 788:40

Waki’ narrated to us, from al-Mas’udi, from ‘Adi ibn Thabit, from Abu Burdah, from Abu Musa, that when Asma’ arrived, ‘Umar ibn al-Khattab (may Allah be pleased with him) met her on one of the roads of Medina and said, "Is she the Abyssinian?" She said, "Yes." He said, "You are an excellent people, were it not that you preceded us in the migration." She said to ‘Umar, "You were with the Messenger of Allah (peace and blessings of Allah be upon him); he would carry your foot-soldiers and teach your ignorant ones, while we fled with our religion. As for me, I will not return until I mention that to the Prophet (peace and blessings of Allah be upon him)." So she returned to him and told him. The Prophet (peace and blessings of Allah be upon him) said, "Rather, you have two migrations: your migration to Medina and your migration to Abyssinia."