Three Main Components of Islam

In addition to Qur'an, there is Sunnah. Sunnah is a compositions of hadiths - stories about Muhammad. Sunni Muslims believe that Sunnah as well as Qur'an is an authority for their faith, worship, and daily living. Not all the hadiths are regarded in the same way. There are reliable, good, and weak hadiths as well as so called known and unknown hadiths. It is defined by the ways of transmission of hadiths and by their contents. There are two books that contain only reliable hadiths - Sahih al-Bukhari and Sahih Muslim. "Sahih" means "reliable", al-Bukhari and Muslim are the names of their authors. There are also other books that contain reliable, good, and weak hadiths.

In order to understand Islam, it is important to know famous hadith of Jibril (Gabriel). There are several variants of this hadith in the beginning of Sahih Muslim. I will quote here the main part of hadith 0001:

He [Abdullah ibn Umar] further said: My father, Umar ibn al-Khattab, told me: One day we were sitting in the company of Allah's Messenger (peace be upon him) when there appeared before us a man dressed in pure white clothes, his hair extraordinarily black. There were no signs of travel on him. None amongst us recognized him. At last he sat with the Messenger (peace be upon him). He knelt before him placed his palms on his thighs and said: Muhammad, inform me about al-Islam. The Messenger of Allah (peace be upon him) said: Al-Islam implies that you testify that there is no god but Allah and that Muhammad is the messenger of Allah, and you establish prayer, pay Zakat, observe the fast of Ramadan, and perform pilgrimage to the (House) if you are solvent enough (to bear the expense of) the journey. He (the inquirer) said: You have told the truth. He (Umar ibn al-Khattab) said: It amazed us that he would put the question and then he would himself verify the truth. He (the inquirer) said: Inform me about Iman (faith). He (the Holy Prophet) replied: That you affirm your faith in Allah, in His angels, in His Books, in His Messengers, in the Day of Judgment, and you affirm your faith in the Divine Decree about good and evil. He (the inquirer) said: You have told the truth. He (the inquirer) again said: Inform me about al-Ihsan (performance of good deeds). He (the Holy Prophet) said: That you worship Allah as if you are seeing Him, for though you don't see Him, He, verily, sees you. He (the enquirer) again said: Inform me about the hour (of the Doom). He (the Holy Prophet) remarked: One who is asked knows no more than the one who is inquiring (about it). He (the inquirer) said: Tell me some of its indications. He (the Holy Prophet) said: That the slave-girl will give birth to her mistress and master, that you will find barefooted, destitute goat-herds vying with one another in the construction of magnificent buildings. He (the narrator, Umar ibn al-Khattab) said: Then he (the inquirer) went on his way but I stayed with him (the Holy Prophet) for a long while. He then, said to me: Umar, do you know who this inquirer was? I replied: Allah and His Messenger know best. He (the Holy Prophet) remarked: He was Gabriel (the angel). He came to you in order to instruct you in matters of religion.

This hadith tells that there are three components of Islam:
1. Iman (faith)
2. Islam (this word here means rituals of worship)
3. Ihsan (sincerity)

There are six main points of faith (Iman):
1. Faith in Allah
2. Faith in His angels
3. Faith in His books (Holy Scriptures)
4. Faith in His messengers and prophets
5. Faith in the Last Day that includes judgment
6. Faith in His predestination of everything good and evil
Every Muslim is obligated to believe in each of these six points.

There are five main points of worship (Islam):
1. Shahadah (confession that there is no god but Allah and that Muhammad is the messenger of Allah)
2. Salah (ritual prayer 5 times a day)
3. Zakat (alms)
4. Sawm (fast at the month of Ramadan)
5. Hajj (pilgrimage to Kaaba in Mecca) if there is physical and financial possibility.
Every Muslim is obligated to believe that all these rituals are important and fulfill all of them unless he or she cannot fulfill them due to some reasons.