Adultery

Adultery is considered a sin in all religions. The Bible decrees the death sentence for both the adulterer and the adulteress (Lev. 20:10) . Islam also equally punishes both the adulterer and the adulteress (Quran 24:2):

“The woman and the man guilty of adultery or fornication,- flog each of them with a hundred stripes: Let not compassion move you in their case, in a matter prescribed by Allah, if ye believe in Allah and the Last Day: and let a party of the Believers witness their punishment.”

However, the Quranic definition of adultery is very different from the Biblical definition. Adultery, according to the Quran, is the involvement of a married man or a married woman in an extramarital affair.

The Bible only considers the extramarital affair of a married woman as adultery (Leviticus 20:10, Deuteronomy 22:22, Proverbs 6:20-7:27):

"If a man is found sleeping with another man's wife, both the man who slept with her and the woman must die. You must purge the evil from Israel" (Deut. 22:22).

"If a man commits adultery with another man's wife both the adulterer and the adulteress must be put to death" (Lev. 20:10).

According to the Biblical definition, if a married man sleeps with an unmarried woman, this is not considered a crime at all. The married man who has extramarital affairs with unmarried women is not an adulterer and the unmarried women involved with him are not adulteresses. The crime of adultery is committed only when a man, whether married or single, sleeps with a married woman. In this case the man is considered adulterer, even if he is not married, and the woman is considered adulteress. In short, adultery is any illicit sexual intercourse involving a married woman. The extramarital affair of a married man is not per se a crime in the Bible. Why is the dual moral standard? According to Encyclopaedia Judaica, the wife was considered to be the husband's possession and adultery constituted a violation of the husband's exclusive right to her; the wife as the husband's possession had no such right to him. 15 That is, if a man had sexual intercourse with a married woman, he would be violating the property of another man and, thus, he should be punished.
To the present day in Israel, if a married man indulges in an extramarital affair with an unmarried woman, his children by that woman are considered legitimate. But, if a married woman has an affair with another man, whether married or not married, her children by that man are not only illegitimate but they are considered bastards and are forbidden to marry any other Jews except converts and other bastards. This ban is handed down to the children's descendants for 10 generations until the taint of adultery is presumably weakened. 

The Quran, on the other hand, never considers any woman to be the possession of any man. The Quran eloquently describes the relationship between the spouses by saying:

" And among His signs is that He created for you mates from among yourselves, that you may dwell in tranquility with them and He has put love and mercy between your hearts: verily in that are signs for those who reflect" (Quran 30:21).

This is the Quranic conception of marriage: love, mercy, and tranquillity, not possession and double standards.

Adapted from an article on IslamiCity called:
Women in Islam Versus Women in the Judaeo-Christian TraditionThe Myth and The Reality
By: Sherif Abdel Azim, Ph.D.- Queens University, Kingston, Ontario, Canada

What does the Qur'an say about Christians?

In the Qur'an, Christians are often referred to as among the "People of the Book," i.e. people who have received and believed in previous revelation from God's prophets. There are verses that highlight the commonalities between Christians and Muslims (those who believe in the oneness of God), and other verses that warn Christians against sliding towards polytheism in their worship of Jesus Christ.

Commonalities:

"Surely those who believe, and those who are Jews, and the Christians, and the Sabians -- whoever believes in God and the Last Day and does good, they shall have their reward from their Lord. And there will be no fear for them, nor shall they grieve" (Chapter 2:Verse 62, Chapter 5:Verse 69, and many other verses of the Glorious Qur’an)

"...and nearest among them in love to the believers will 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" (Chapter 5, Verse 82 of the Qur’an).

"O you who believe! Be helpers of God -- as Jesus the son of Mary said to the Disciples, 'Who will be my helpers in (the work of) God?' Said the disciples, 'We are God's helpers!' Then a portion of the Children of Israel believed, and a portion disbelieved. But We gave power to those who believed, against their enemies, and they became the ones that prevailed" (Chapter 6, Verse 14).

Warnings:

"If only they [i.e. Christians] had stood fast by the Law, the Gospel, and all the revelation that was sent to them from their Lord, they would have enjoyed happiness from every side. There is from among them a party on the right course, but many of them follow a course that is evil" (5:66).

"Oh People of the Book! Commit no excesses in your religion, nor say of God anything but the truth. Christ Jesus, the son of Mary, was (no more than) a messenger of God, and His Word which He bestowed on Mary, and a spirit proceeding from Him. So believe in God and His messengers. Say not, 'Trinity.' Desist! It will be better for you, for God is One God, 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 God as a Disposer of affairs" (Chapter 4, Verse  171).

"The Jews call 'Uzair a son of God, and the Christians call Christ the son of God. That is but a saying from their mouth; (in this) they but imitate what the unbelievers of old used to say. God's curse be on them; how they are deluded away from the Truth! They take their priests and their anchorites to be their lords in derogation of God, and (they take as their Lord) Christ the son of Mary. Yet they were commanded to worship but One God: there is no god but He. Praise and glory to Him! (Far is He) from having the partners they associate (with Him)" (Chapter 9, Verse 30 and 31).

http://islam.about.com/cs/jesus/f/christians.htm