Hazrat Umar (Allah be pleased with him) said: One day while we were sitting with the Messenger of Allah (peace be upon him) there appeared before us a man whose clothes were exceedingly white and whose hair was exceedingly black; no signs of journeying were to be seen on him and none of us knew him. He walked and sat down by the Prophet (peace be upon him). Resting his knees against his and placing the palm of his hands on his thigh, he said: O Muhammad, tell me about Islam. The Messenger of Allah (peace be upon him) said: Islam is to testify that there is no god but Allah and Muhammad is the Messenger of Allah, to perform the prayers, to pay the zakat , to fast in Ramadan, and to make the pilgrimage to the House if you are able to do so. He said: You have spoken rightly, and we were amazed at him asking him and saying that he had spoken right. He said: Then tell me about iman . The Prophet (may the blessings and peace of Allah be upon him ) said: It is to believe in Allah, His angels, His books, His messengers and the Last Day, and to believe in divine destiny, both the good and evil thereof. He said: You have spoken rightly. He said: Then tell me about ihsan , The Prophet (may the blessings and peace of Allah be upon him ) said: It is to worship Allah as though you are seeing Him, and while you see Him not yet truly He sees you. He said then tell me about the Hour , The Prophet (peace be upon him) said: The one questioned about it knows no better than the questioner. He said: Tell me about its signs. The Prophet (peace be upon him) said: The slave-girl will give birth to her mistress and that you will see the barefooted naked, destitute herdsmen competing in constructing lofty buildings. Then he took himself off and I stayed for a time. Then the Prophet (may the blessings and peace of Allah be upon) said: O Umar, do you know who the questioner was? I said: Allah and hid Messenger know best. The Prophet (peace be upon him) said: It was Gabriel, who came to you to teach you your religion.