"Islam is built upon five things; testimony that there is no god but God and that Muhammad is the Apostle of God. Prayer (salat), the Poor-rate (zakat), Pilgrimage (hajj) and Fast (sawm) in Ramadan."
Jibril came in the form of an Arab of the desert and sat down so that his knees touched the knees of the Prophet and said, "O Apostle of God, what is Islam?" He said, "That thou should bear witness that there is no god save God and
that I am the Apostle of God; that thou shouldest perform the prayers (salat) and bring the poor-rate (zakat) and fast in the month of Ramadan and pilgrimage to the House if the way is possible for thee." He said, "Thou hast spoken truly." Then he said, "What is Faith (iman)?" The Prophet said, "That thou should believe in God and His angels and His cooks and His messengers and in the Last Day, and that thou should believe in the decreeing (qadar) both of good and of evil." He said, "Thou hast spoken truly." Then he said, "What is right doing (ihsan)?" The Prophet said, "That thou should serve God as though thou sawest Him; for though thou seest Him not, He sees thee." He said, "Thou hast spoken truly." Then he said, "When shall be the Last Day (as-sa‘a)?" The Prophet said, "The questioned knoweth not more of that than the questioner." Then he arose and went out. And the Prophet said, "That was Jibril; he came to you to teach you your religion (din)."--Translated from Cureton's text of ash-Shahrastani, p. 27.