Sayyiduna Zayd bin Thabit (may Allah be pleased with him) narrates that the Messenger of Allah (peace and blessings be upon him) said: "Apart from Uthman and Ruqayyah, there was no emigrant after Lot (peace be upon him)." Meaning: the two of them (Uthman and Ruqayyah, may Allah be pleased with them both) were the very first of those who emigrated to Abyssinia.
Hadith Referenceالمعجم الكبير للطبراني / باب الزاي / 4862