Islam teaches us that Muslims will be rewarded in proportion to their good deeds, their restraint from evil deeds, and their faith. In this manner we will have people who will enter different levels of heaven, as well as different levels of hell, in direct proportion to their faith and deeds.
We learn about the laws of Islam from the Qur'an and the Sunnah. The Qur'an is the Holy book of Islam which contains the words of Allah Almighty and the broad guidelines of Islam. The Sunnah, is the traditions of the prophet Muhammad (pbuh) which included both his words and his actions.
The Sunnah usually provides the details for those laws which are drawn out in broad outlines in the Qur'an. Each one of these two sources has a dedicated and very complex science associated with it.
"And We have sent down unto you (O Muhammad) the Reminder (one of the names of the Qur'an), that you may clarify to mankind that which was sent down to them" The noble Qur'an, Al-Nahil(16):44
Al-Bukhari narrated upon the authority of Abu Hurairah, that he said: Allah's Messenger (peace be upon him) said:
"Allah said: 'I will declare war against him who shows hostility to a pious worshipper of Mine. And the most beloved things with which My slave draws nearer to Me is that which I have ordained upon him. My slave continues to draw closer to Me through performing 'Nawafil' (supplementary worship) till I love him.
So I become the sense of hearing with which he hears, and the sense of sight with which he sees, and the hand with which he grips, and the leg with which he walks. And if he asks Me, I will give him, and if he asks my protection, I will protect him'"