We believe that this religion is the religion Jibrīl brought down to Muhammad (may Allah's peace and blessings be upon him), and it has three degrees: Islam, Imān, and ihsān. Each of these has its own pillars. ‘Umar ibn al-Khattāb (may Allah be pleased with him) reported: While we were sitting with the Messenger of Allah (may Allah’s peace and blessings be upon him) one day, a man who had an extremely white garment on, who had extremely black hair, and who did not have any traces of travel, came to us. None of us knew him. He sat with the Prophet (may Allah’s peace and blessings be upon him) so close that his knees touched his knees. He placed his hands on his thighs and said: "O Muhammad, tell me about Islam." The Messenger of Allah (may Allah’s peace and blessings be upon him) said: "Islam is to testify that none is worthy of being worshiped except Allah and that Muhammad is the Messenger of Allah, establish prayer, give Zakah, fast Ramadan, and perform Hajj, if you are able to." The man said: "You have spoken the truth." We were amazed by him; asking him, then declaring him as having told the truth. Then, he said: "Tell me about Imān (faith)." The Messenger of Allah (may Allah’s peace and blessings be upon him) said: "It is to believe in Allah, His angels, books, messengers, the Last Day, and destiny, the pleasant and unpleasant aspects thereof." The man said: "You have spoken the truth. Tell me about ihsān." The Prophet (may Allah’s peace and blessings be upon him) said: "It is to worship Allah as if you see Him. If you cannot see Him, He surely sees you." The man said: "Tell me about the Hour." The Prophet (may Allah’s peace and blessings be upon him) said: "The one being asked is no more knowledgeable than the one asking." The man said: "Tell me about its signs." The Prophet (may Allah’s peace and blessings be upon him) said: "It is when a slave girl gives birth to her master, and when you find barefoot, naked, poor shepherds competing in making buildings." Then, he left, and I remained for a short while. Then, the Messenger of Allah (may Allah’s peace and blessings be upon him) said: "O ‘Umar, do you know who that questioner was?" I said: "Allah and His Messenger know best." He said: "That was Jibrīl, who came to teach you your religion." [Narrated by Muslim (8), Abu Dāwūd (4695), At-Tirmidhi (2610), An-Nasā’i (4990), and Ibn Mājah (63)]
The Prophet (may Allah's peace and blessings be upon him) also outlined the pillars of Islam in other Hadīths. He said: "Islam was built on five pillars: testifying that none is worthy of being worshiped except Allah and that Muhammad is the Messenger of Allah, establishing prayer, giving Zakah, performing Hajj, and fasting Ramadan.” [Narrated by Al-Bukhāri (8), Muslim (16), At-Tirmidhi (2609), and An-Nasā’i (5001)] Talhah ibn ‘Ubaydullāh (may Allah be pleased with him) reported: A man from among the people of Najd with disheveled hair came to the Messenger of Allah (may Allah's peace and blessings be upon him). The humming sound of his voice could be heard but what he was saying could not be understood. He came closer and it was then known that he was asking about Islam. The Messenger of Allah (may Allah's peace and blessings be upon him) said: "Five prayers each day and night." He asked: "Do I have to observe anything else?" He replied: "No, unless you do it voluntarily." The Messenger of Allah (may Allah's peace and blessings be upon him) said: "And fasting Ramadan." He asked: "Do I have to observe anything else?" He replied: "No, unless you do it voluntarily." The Messenger of Allah (may Allah's peace and blessings be upon him) mentioned Zakah to him, and he asked: "Do I have to pay anything else?" He replied: "No, unless you do it voluntarily." The man then turned away saying: "I swear by Allah, I will not add anything to this or fall short of it." Thereupon, the Messenger of Allah (may Allah's peace and blessings be upon him) said: "He will be successful if he speaks the truth." [Narrated by Al-Bukhāri (46), Muslim (11), Abu Dāwūd (391), and An-Nasā’i (458)]
And Allah Almighty says: {And they were commanded not, but they should worship Allah with sincere devotion to Him, being inclined to true faith, and to establish prayer and give Zakah; that is the true religion.} [Surat al-Bayyinah: 5] He also says: {But if they repent, establish prayers and give Zakah, then set them free, for Allah is All-Forgiving, Most Merciful.} [Surat at-Tawbah: 5] And He, Exalted be He, says {Yet if they repent, establish prayer and give Zakah, then they are your brothers in faith.} [Surat at-Tawbah: 11] And the Prophet (may Allah's peace and blessings be upon him) said: "I have been ordered to fight the people until they testify that none is worthy of being worshiped except Allah and that Muhammad is the Messenger of Allah, establish prayer, and give Zakah. If they do so, then their wealth and blood are protected from me except through the right of Islam, and their reckoning is with Allah." [Narrated by Al-Bukhāri (25) and Muslim (22)]
Abu Mūsa (may Allah be pleased with him) reported: "O Messenger of Allah, which Islam is best?" He said: "He from whose tongue and hands Muslims are safe." [Narrated by Al-Bukhāri (11), Muslim (42), At-Tirmidhi (2504), and An-Nasā’i (4999)]
In another Hadīth, the Prophet (may Allah's peace and blessings be upon him) said: "If a person embraces Islam sincerely, Allah forgives all his past sins, after which starts the settlement of accounts: The reward of a good deed will be ten times to seven hundred times as much, and a sin will be recorded as it is, unless Allah forgives it." [Narrated by Al-Bukhāri as mu‘allaq (41) and An-Nasā’i (4998)]