Christians and Islam
"...and nearest among them (men) in love to the believers wilt you 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. And when they listen to the revelation received by the messenger, you wilt see their eyes overflowing with tears for they recognize the truth: They pray: 'Our lord! we believe; write us down among the witnesses'." Al-Maidah(5):82-83.
The relationship of Islam and the Qur'an to the previous messages and scriptures
"And unto you (O Muhammad) have We revealed the Scripture with the truth, confirming whatever Scripture was before it, and a watcher/corrector over it. So judge between them by that which Allah has revealed, and follow not their desires away from the truth which has come unto you. For each We have appointed a divine law and a traced out way. Had Allah willed He could have made you one community. But that He may try you by that which He has given you (He has made you as you are). So vie one with another in good works. Unto Allah you will all return, and He will then inform you of that wherein you differ. So judge between them by that which Allah has revealed, and follow not their desires, but beware of them lest they seduce you from some part of that which Allah has revealed unto you. And if they turn away, then know that Allah's will is to smite them for some sin of theirs. Lo! many of mankind are rebellious." Al-Maidah(5):48-49