Umar bin Khattab reported,

While we were sitting with the Messenger of Allah ﷺ one day, a man suddenly appeared before us. His clothes were strikingly white, his hair intensely black, and no trace of travel could be seen on him, yet none of us recognized him. He went up to the Messenger of Allah ﷺ and sat down before him, resting his knees against the Prophet's knees and placing his palms on his own thighs.Then he said, "Muhammad, tell me about Islam."The Messenger of Allah ﷺ replied, "Islam is to bear witness that there is no god but Allah and that Muhammad is the Messenger of Allah, to establish the prayer, to give the zakat, to fast Ramadan, and to make the pilgrimage to the House if you are able to find a way."The man said, "You have spoken truly."We were astonished at him, questioning the Prophet and then confirming his answers.Then he said, "Tell me about iman."The Prophet replied, "It is to believe in Allah, His angels, His books, His messengers, the Last Day, and to believe in divine decree, both its good and its evil."The man said, "You have spoken truly. Now tell me about ihsan."The Prophet replied, "It is to worship Allah as though you see Him, for though you do not see Him, He sees you."The man said, "Then tell me about the Hour."The Prophet replied, "The one being asked knows no more about it than the one asking."The man said, "Then tell me about its signs."The Prophet replied, "That a slave-girl will give birth to her mistress, and that you will see barefoot, naked, destitute shepherds competing with one another in constructing tall buildings."Umar said, "Then he departed, and I remained for three days. After that, the Messenger of Allah ﷺ said to me, 'Umar, do you know who the questioner was?'I said, 'Allah and His Messenger know best.'He said, 'That was Jibreel . He came to teach you your religion.'"

أخبرنا إسحق بن إبراهيم قال حدثنا النضر بن شميل قال أنبأنا كهمس بن الحسن قال حدثنا عبد الله بن بريدة عن يحيى بن يعمر أن عبد الله بن عمر قال

حدثني عمر بن الخطاب قال

بينما نحن عند رسول الله ﷺ ذات يوم إذ طلع علينا رجل شديد بياض الثياب شديد سواد الشعر لا يرى عليه أثر السفر ولا يعرفه منا أحد حتى جلس إلى رسول الله ﷺ فأسند ركبتيه إلى ركبتيه ووضع كفيه على فخذيه ثم قال يا محمد أخبرني عن الإسلام قال أن تشهد أن لا إله إلا الله وأن محمدا رسول الله وتقيم الصلاة وتؤتي الزكاة وتصوم رمضان وتحج البيت إن استطعت إليه سبيلا قال صدقت فعجبنا إليه يسأله ويصدقه ثم قال أخبرني عن الإيمان قال أن تؤمن بالله وملائكته وكتبه ورسله واليوم الآخر والقدر كله خيره وشره قال صدقت قال فأخبرني عن الإحسان قال أن تعبد الله كأنك تراه فإن لم تكن تراه فإنه يراك قال فأخبرني عن الساعة قال ما المسئول عنها بأعلم بها من السائل قال فأخبرني عن أماراتها قال أن تلد الأمة ربتها وأن ترى الحفاة العراة العالة رعاء الشاء يتطاولون في البنيان قال عمر فلبثت ثلاثا ثم قال لي رسول الله ﷺ يا عمر هل تدري من السائل قلت الله ورسوله أعلم قال فإنه جبريل عليه السلام أتاكم ليعلمكم أمر دينكم