During this period, 'Umar Ibn Al-Khattab adopted Islam. In him the new faith gained a valuable adherent and an important factor in the future development and propagation of Islam.
Hitherto he had been a violent opposer of the Prophet and a bitter enemy of Islam. His conversion is said to have been worked by the miraculous effect on his mind of a surah of the Qur'an which his sister was reading in her house, where he had gone with the intention of killing her for adopting Islam. Thus the party of the Prophet had been strengthened by the conversion of his uncle Hamza, a man of great valor and merit; and of Abu Bakr and Umar, both men of great energy and reputation. The Muslims now ventured to perform their devotions in public.