Sahih al-Bukhari 3864
Merits of the Helpers in Madinah (Ansaar)
The conversion ‘Umar رضي الله عنه to Islam
Narrated `Abdullah bin `Umar: While `Umar was at home in a state of fear, there came Al-`As bin Wail As-Sahmi Abu `Amr, wearing an embroidered cloak and a shirt having silk hems. He was from the tribe of Bani Sahm who were our allies during the pre-Islamic period of ignorance. Al-`As said to `Umar "What is wrong with you?" He said, "Your people claim that they would kill me if I become a Muslim." Al-`As said, "Nobody will harm you after I have given protection to you." So Al-`As went out and met the people streaming in the whole valley. He said, "Where are you going?" They said, "We want Ibn Al-Khattab who has embraced Islam." Al-`As said, "There is no way for anybody to touch him." So the people retreated.