Sayyiduna Umar (may Allah be pleased with him) narrates: One day we were sitting in the company of the Prophet (peace and blessings be upon him) when suddenly a man came walking. He was dressed in strong, white clothes and had extremely black hair. There were no signs of travel visible on him, nor did any of us recognize him. That man came and sat near the Prophet (peace and blessings be upon him). He joined his knees with the knees of the Prophet (peace and blessings be upon him) and placed his hands on the thighs of the Prophet (peace and blessings be upon him) and said, "O Muhammad (peace and blessings be upon him)! Tell me about Islam, what is Islam?" The Prophet (peace and blessings be upon him) replied: "To bear witness that there is no deity except Allah and that Muhammad (peace and blessings be upon him) is the Messenger of Allah, to establish prayer, to give zakat, to fast in Ramadan, and to perform Hajj to the House of Allah." He affirmed (the words of the Prophet, peace and blessings be upon him), so we were amazed at his questioning and then confirming. He then asked, "What is Iman (faith)?" The Prophet (peace and blessings be upon him) replied: "That you believe in Allah, His angels, His books, His messengers, the Last Day, and in destiny, both its good and its bad." He said, "You have spoken the truth." Then he asked, "What is Ihsan (excellence)?" The Prophet (peace and blessings be upon him) replied: "That you worship Allah as if you see Him, and if you cannot see Him, then (know that) He surely sees you (so always keep in mind that Allah is watching us)." He then asked, "When will the Hour (Day of Judgment) come?" The Prophet (peace and blessings be upon him) replied: "The one being questioned knows no more about it than the questioner (meaning, both of us are unaware in this matter)." He said, "Then tell me some of its signs." The Prophet (peace and blessings be upon him) replied: "When you see those who were barefoot, naked, and destitute—shepherds—competing in constructing tall buildings, and when slave women give birth to their mistresses, then the Hour is near." Then that man left, and after a while, the Prophet (peace and blessings be upon him) said to me, "O Umar! Do you know who that questioner was?" I replied, "Allah and His Messenger know best." He said, "That was Jibreel (Gabriel, peace be upon him), who came to teach you the important matters of your religion."