The Hadith of Gabriel
Sachiko Murata, and William Chittick cite a version of the Hadith of Gabriel in their book, The Vision of Islam - here is a section of this hadith attributed to our Prophet.
'Umar ibn al-Khattab said: One day when we were with God's messenger, a man with very white clothing and very black hair came up to us. No mark of travel was visible on him, and none of us recognized him. Sitting down before the Prophet, leaning his knees against his, and placing his hands on his thighs, he said, "Tell me, Muhammad, about Islam." (Chittick/Murata use the word submission)
The Prophet replied, "Islam means that you should bear witness that there is no god but God and that Muhammad is God's messanger, that you should perform the ritual prayer, pay the alms tax, fast during Ramadan, and make the pilgrimage to the House if you are able to go there."
The man said, "You have spoken the truth." We were surprised at his questioning him and then declaring that he had spoken the truth. He said, Now tell me about faith (Iman)"
The Prophet replied, "Faith means that you have faith in God, the angels, the Books, the messengers, and the Last Day, and that you have faith in the measuring out, both its good and its evil."
Remarking that he had spoken the truth, he then said, "Now tell me about doing what is beautiful (Ihsan).
The Prophet replied, "Doing what is beautiful means that you should worship God as if you see God, for even if you do not see God, God sees you."
"Invite (all) to the Way of thy Lord with wisdom and beautiful preaching; and argue with them in ways that are best and most gracious." Noble Qur'ân 16:125