“One day we were sitting in the company of the Messenger of Allah, peace and blessings 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 of us recognized him. He sat with the Prophet, peace and blessings be upon him. Resting his knees against his and the palms of his hands on his thighs, he said, ‘O Muhammad, tell me about Islam’. 
The Messenger of Allah replied, ‘Islam is to testify that there is no god but Allah and that Muhammad is the Messenger of Allah, to establish the prayer, pay the zakat, observe the fast of Ramadan, and perform the pilgrimage to the House if you are able to do so’. 
He said, ‘You have spoken the truth,’ and we were amazed at him asking and then verifying that he had spoken the truth. He then said, ‘Inform me about Iman’.
He replied, ‘It is to believe in Allah, His angels, His books, His messengers, the Last Day, and in the divine destiny of both good and evil’. 
He said, ‘You have spoken the truth’. 
He then said, ‘Tell me about Ihsan’. 
He said, ‘It is to worship Allah as if you see Him, for though you do not see Him, surely He sees you’. 
He then said, ‘Inform me about the Hour’. 
He replied, ‘The one who is asked knows no more than the one who is asking’. 
He said, ‘Tell me some of its signs’. 
He said, ‘That the slave-girl will give birth to her mistress, and barefoot, destitute shepherds will compete with one another in the building of magnificent buildings’.
Then he (the questioner) went on his way but I stayed with him (the Prophet) for a long while. 
He said to me, ‘Umar, do you know who this questioner was?’ 
I replied, ‘Allah and His Messenger know best’. 
He said, ‘He was Gabriel. He came to instruct you in your religion’.”