THE FOLLOWING are verses from the Quran explaining why a Muslim may not become heterodox. To read the Quran for yourself, see our recommended versions and save yourself hours of frustration: Read the Koran. To read about the distinction between orthodox Muslims and heterodox Muslims, click here.
10:61 Whatever business you are in, or whatever you read from the Koran, or whatever you do, We will be witnesses over you. Not the weight of an atom on earth or in heaven is concealed from the Lord. But the least and the greatest of these things are recorded clearly in the book [the book of life’s deeds].
10:62 The friends of Allah will have no fear, nor shall they be put to grief. Those who believe and fear Allah will receive good tidings in this life, and in the next. There is no changing the words of Allah. This is the great triumph. And do not let their [the Meccans] speech grieve you for all power belongs to Allah. He is the hearer and the knower.
10:66 Surely, whatever is in the heavens and the earth belongs to Allah. What do they follow who worship others beside Allah? They follow only guesses, and they are but liars. He has appointed the night so you can rest, and the day to make things visible. These are signs for those who hear.
10:68 They [Christians] say, “Allah has begotten a son. Glory be to Him. He is the self-sufficient. His is all that is in the heavens and the earth.” You have no authority for that claim. Do you say things of Allah that you do not know? Say: They who devise a lie against Allah will not prosper. A portion of the world for a time will be theirs. Then they return to Us. Then We will make them taste the severest torment because they were unbelievers.
45:14 Tell the believers to forgive those who do not hope for the days of Allah. It is up to Him to reward men according to their actions. Whoever does good, does so for their own soul, and whoever does wrong, does so against themselves. In the end, you will be brought back to your Lord.
Read more on this important injunction.