Sahih al-Bukhari 3865
Narrated `Abdullah bin `Umar:
When `Umar embraced Islam, all The (disbelieving) people gathered around his home and said, 
"`Umar has embraced Islam." At that time I was still a boy and was on the roof of my house. There 
came a man wearing a cloak of Dibaj (i.e. a kind of silk), and said, "`Umar has embraced Islam. 
Nobody can harm him for I am his protector." I then saw the people going away from `Umar and 
asked who the man was, and they said, "Al-`As bin Wail."
حَدَّثَنَا عَلِيُّ بْنُ عَبْدِ اللَّهِ، حَدَّثَنَا سُفْيَانُ، قَالَ عَمْرُو بْنُ دِينَارٍ سَمِعْتُهُ قَالَ قَالَ عَبْدُ اللَّهِ بْنُ عُمَرَ ـ رضى الله عنهما ـ لَمَّا أَسْلَمَ عُمَرُ اجْتَمَعَ النَّاسُ عِنْدَ دَارِهِ وَقَالُوا صَبَا عُمَرُ‏.‏ وَأَنَا غُلاَمٌ فَوْقَ ظَهْرِ بَيْتِي، فَجَاءَ رَجُلٌ عَلَيْهِ قَبَاءٌ مِنْ دِيبَاجٍ فَقَالَ قَدْ صَبَا عُمَرُ‏.‏ فَمَا ذَاكَ فَأَنَا لَهُ جَارٌ‏.‏ قَالَ فَرَأَيْتُ النَّاسَ تَصَدَّعُوا عَنْهُ فَقُلْتُ مَنْ هَذَا قَالُوا الْعَاصِ بْنُ وَائِلٍ‏.‏