Umar ibn al-Khattab, a companion of the prophet, said:
"One day we were sitting in the company of Allah's Apostle (peace be upon him) when there appeared before us a man dressed in pure white clothes, his hair extraordinarily black.

There were no signs of travel on him. None amongst us recognized him. At last he sat with the Apostle (peace be upon him).

He knelt before him placed his palms on his thighs and said: Muhammad, inform me about Islam.