Also on the authority of ‘Umar, radiyallahu ‘anhu, who said:
“While we were one day sitting with the Messenger of Allaah, sallAllaahu ‘alayhi wasallam, there appeared before us a man dressed in extremely white clothes and with very black hair. No traces of journeying were visible on him, and none of us knew him.
He sat down close by the Prophet, sallAllaahu ‘alayhi wasallam, rested his knee against his thighs, and said, O Muhammad! Inform me about Islaam.” Said the Messenger of Allaah, sallallaahu ‘alayhi wasallam, “Islaam is that you should testify that there is no deity save Allaah and that Muhammad is His Messenger, that you should perform salaah (ritual prayer), pay the zakah, fast during Ramadaan, and perform Hajj (pilgrimage) to the House (the Ka’bah at Makkah), if you can find a way to it (or find the means for making the journey to it).” Said he (the man), “You have spoken truly.”
We were astonished at his thus questioning him and telling him that he was right, but he went on to say, “Inform me about Imaan (faith).” He (the Messenger of Allaah) answered, “It is that you believe in Allaah and His angels and His Books and His Messengers and in the Last Day, and in fate (qadar), both in its good and in its evil aspects.” He said, “You have spoken truly.”
Then he (the man) said, “Inform me about Ihsaan.” He (the Messenger of Allaah) answered, ” It is that you should serve Allaah as though you could see Him, for though you cannot see Him yet He sees you.” He said, “Inform me about the Hour.” He (the Messenger of Allaah) said, “About that the one questioned knows no more than the questioner.” So he said, “Well, inform me about the signs thereof (i.e. of its coming).” Said he, “They are that the slave-girl will give birth to her mistress, that you will see the barefooted ones, the naked, the destitute, the herdsmen of the sheep (competing with each other) in raising lofty buildings.” Thereupon the man went off.
I waited a while, and then he (the Messenger of Allaah) said, “O ‘Umar, do you know who that questioner was?” I replied, “Allaah and His Messenger know better.” He said, “That was Jibreel. He came to teach you your religion.””
This hadeeth contains everything about Islaam, the 5 pillars of Islaam, the beliefs that make up eemaan (inc. the belief of fate/qadar), the attainment of the highest level of Eemaan which is Ihsaan, the adab of seeking knowledge and teaching.
This article can be read in full and with more detail at the following link: http://fortyhadith.iiu.edu.my/hadith02.htm