In Islam, Christians are idolators because they believe in the Trinity and the deity of Christ.  Islam says the Trinity is three gods.  But, that is a misrepresentation of the biblical doctrine. Also, Muslims say that Christians are unbelievers who have corrupted the Bible and deny the truth of Allah. Islam teaches that Christians, along with Jews, Christians are the enemies of God and eventually must submit to Allah or face eternal damnation.  This is, of course, the teaching of Muhammad who only had a partial understanding of Christianity and made errors in writing about it.

1. Christians are compassionate and merciful
   1. Surah 57:27, “Then, in their wake, We followed them up with (others of) Our apostles: We sent after them Jesus the son of Mary, and bestowed on him the Gospel; and We ordained in the hearts of those who followed him Compassion and Mercy. But the Monasticism which they invented for themselves, We did not prescribe for them: (We commanded) only the seeking for the Good Pleasure of Allah; but that they did not foster as they should have done. Yet We bestowed, on those among them who believed, their (due) reward, but many of them are rebellious transgressors.”
2. Are nearest to friendship with Muslims
   1. Surah 5:82, Strongest among men in enmity to the believers wilt thou find the Jews and Pagans; and nearest among them in love to the believers wilt thou find those who say, “We are Christians”: because amongst these are men devoted to learning and men who have renounced the world, and they are not arrogant.”
3. Are not true believers because they believe in the deity of Christ
   1. Surah 5:17, “In blasphemy indeed are those that say that Allah is Christ the son of Mary. Say: “Who then hath the least power against Allah, if His will were to destroy Christ the son of Mary, his mother, and all every—one that is on the earth? For to Allah belongeth the dominion of the heavens and the earth, and all that is between. He createth what He pleaseth. For Allah hath power over all things.”
4. Are unbelievers
   1. Surah 98:6, “Those who reject (Truth), among the People of the Book and among the Polytheists, will be in Hell-Fire, to dwell therein (for aye). They are the worst of creatures.”
5. Are wrong for believing in the Trinity
   1. Surah 4:171, “O People of the Book! Commit no excesses in your religion: Nor say of Allah aught but the truth. Christ Jesus the son of Mary was (no more than) an apostle of Allah, and His Word, which He bestowed on Mary, and a spirit proceeding from Him: so believe in Allah and His apostles. Say not “Trinity”: desist: it will be better for you: for Allah is one Allah: Glory be to Him: (far exalted is He) above having a son. To Him belong all things in the heavens and on earth. And enough is Allah as a Disposer of affairs.”
6. Ask Christians if in doubt about the Quran
   1. Surah 10:94, “If thou were in doubt as to what We have revealed unto thee, then ask those who have been reading the Book from before thee: the Truth hath indeed come to thee from thy Lord: so be in no wise of those in doubt.”
7. Call Jesus the son of Allah
   1. Surah 9:30, “The Jews call ‘Uzair a son of Allah, and the Christians call Christ the son of Allah. That is a saying from their mouth; (in this) they but imitate what the unbelievers of old used to say. Allah’s curse be on them: how they are deluded away from the Truth!”
8. Changed and distorted the Scriptures
   1. Narrated Ubaidullah: Ibn ‘Abbas said, “Why do you ask the people of the scripture about anything while your Book (Quran) which has been revealed to Allah’s Apostle is newer and the latest? You read it pure, undistorted and unchanged, and Allah has told you that the people of the scripture (Jews and christians) changed their scripture and distorted it, and wrote the scripture with their own hands and said, ‘It is from Allah,’ to sell it for a little gain. Does not the knowledge which has come to you prevent you from asking them about anything? No, by Allah, we have never seen any man from them asking you regarding what has been revealed to you!”  (Sahih Bukhari, Book #92, Hadith #461)
9. Condemned for worshipping Jesus
   1. “…Then the Christians would be summoned and it would be said to them: What did you worship? They would say: We worshipped Jesus, son of Allah. It would be said to them: You tell a lie; Allah did not take for Himself either a spouse or a son. Then it would be said to them: What do you want? They would say: Thirsty we are, O our Lord! Quench our thirst. They would be directed (to a certain direction) and asked: Why don’t you go there to get water? But they would be pushed and gathered together towards the Hell, which was like a mirage to them, and the flames would consume one another. They would fall Into the Fire, till no one is left except he who worshipped Allah, be he pious or sinful…” (Sahih Muslim, Book #001, Hadith #0352).
10. Cursed because they made the graves of their apostles places of worship
    1. “Abu Huraira reported: The Messenger of Allah (may peace be upon him) said: Let there be curse of Allah upon the Jews and the christians for they have taken the graves of their apostles as places of worship.  (Book #004, Hadith #1081)
11. Do not take Christians as friends
    1. Surah 5:51, “O ye who believe! Take not the Jews and the Christians for your friends and protectors: They are but friends and protectors to each other. And he amongst you that turns to them (for friendship) is of them. Verily Allah guideth not a people unjust.”
12. Do the opposite of what Christians do
    1. “Narrated Abu Huraira : The Prophet said, “Jews and Christians do not dye their hair so you should do the opposite of what they do.”  (Sahih Bukhari, Book #72, Hadith #786)
13. Don’t greet Christians, force them to the narrowest part of the road
    1. “Abu Huraira reported Allah’s Messenger (may peace be upon him) as saying: Do not greet the Jews and the Christians before they greet you and when you meet any one of them on the roads force him to go to the narrowest part of it.  (Book #026, Hadith #5389)
14. Have gone astray
    1. “Narrated Abu Huraira: Allah’s Apostle said, “Say Amen’ when the Imam says “Ghair-il-maghdubi ‘alaihim wala-ddal-lin; not the path of those who earn Your Anger (such as Jews) nor of those who go astray (such as Christians); all the past sins of the person whose saying (of Amin) coincides with that of the angels, will be forgiven.”  (Sahih Bukhari, Book #12, Hadith #749)
15. Have the scriptures from God
    1. Surah 5:68, “Say: “O People of the Book! Ye have no ground to stand upon unless ye stand fast by the Law, the Gospel, and all the revelation that has come to you from your Lord.” It is the revelation that cometh to thee from thy Lord, that increaseth in most of them their obstinate rebellion and blasphemy. But sorrow thou not over (these) people without Faith.”
16. Will have their reward
    1. Surah 2:62, “Those who believe (in the Qur’an), and those who follow the Jewish (scriptures), and the Christians and the Sabians – any who believe in Allah and the Last Day, and work righteousness, shall have their reward with their Lord; on them shall be no fear, nor shall they grieve.”