Musannaf Ibn Abi Shayba 34:152

Ja'far ibn 'Awn narrated to us, from Ibrahim ibn Isma'il ibn Mujammi', he said: Al-Zuhri narrated to me, from Qabisah ibn Dhu'ayb, that Abu Salamah was the son of the paternal aunt of the Messenger of Allah, may Allah bless him and grant him peace. And he was the first to migrate with his wife to the land of Abyssinia, then to Medina.