Modern Islam's scholars say that Quran 65:4 teaches that Muslim men can have a girl as a wife. Sayyid Abul Ala Maududi (d. 1979) in Tafhim al Quran (Commentary on the Quran) interprets verse 65:4 as:

And if you are in doubt about those of your women who have despaired of menstruation, (you should know that) their waiting period is three months, and the same applies to those who have not menstruated as yet. They may not have menstruated as yet either because of young age, or delayed menstrual discharge as it happens in the case of some women, or because of no discharge at all throughout life which, though rare, may also be the case. In any case, the waiting-period of such a woman is the same as of the woman, who has stopped menstruation that is three months from the time divorce was pronounced.

Here, one should bear in mind the fact that according to the explanations given in the Quran the question of the waiting period arises in respect of the women with whom marriage may have been consummated, for there is no waiting-period in case divorce is pronounced before the consummation of marriage. (Al-Ahzab: 49). Therefore, making mention of the waiting-period for the girls who have not yet menstruated, clearly proves that it is not only permissible to give away the girl in marriage at this age but it is also permissible for the husband to consummate marriage with her. Now, obviously no Muslim has the right to forbid a thing which the Quran has held as permissible.

Quran according to teaching of Islam allows pedophilia (adult-child sex). This doesn't mean that every Muslim accepts adult-child sex, but that Quran allows sex between an adult and a child.

Islam question & answer site: It was narrated from ‘Aa’ishah (may Allaah be pleased with her) that the Prophet (peace and blessings of Allaah be upon him) married her when she was six years old, he consummated the marriage with her when she was nine and she stayed with him for nine years. ... The fact that it is permissible to marry a young girl does not mean that it is permissible to have intercourse with her; rather that should not be done until she is able for it. For that reason the Prophet (peace and blessings of Allaah be upon him) delayed the consummation of his marriage to ‘Aa’ishah. Al-Nawawi said: With regard to the wedding-party of a young married girl at the time of consummating the marriage, if the husband and the guardian of the girl agree upon something that will not cause harm to the young girl, then that may be done. If they disagree, then Ahmad and Abu ‘Ubayd say that one a girl reaches the age of nine then the marriage may be consummated even without her consent, but that does not apply in the case of who is younger. Maalik, al-Shaafa’i and Abu Haneefah said: the marriage may be consummated when the girl is able for intercourse, which varies from one girl to another, so no age limit can be set. This is the correct view. There is nothing in the hadeeth of ‘Aa’ishah to set an age limit, or to forbid that in the case of a girl who is able for it before the age of nine, or to allow it in the case of a girl who is not able for it and has reached the age of nine. Al-Dawoodi said: ‘Aa’ishah (may Allaah be pleased with her) was reached physical maturity (at the time when her marriage was consummated).  

On the faith of Islam consummation means that a Muslim man can practice sex with his wife. Religion of Islam teaches that a Muslim can have sex with his wife when she turns nine years.

Dr. Ah­mad Al-Mu’bi Saudi marriage officiant: Marriage is actually two things: First, we are talking about the marriage contract itself. This is one thing, while consummating the marriage - having sex with the wife for the first time - is another thing. There is no minimal age for entering marriage. You can have a marriage contract even with a one-year-old girl, not to mention of nine, seven or eight. This is  merely a contract (indicating) consent. The guardian in a such case must be the father, because the father's opinion is obligatory. Thus, the girl becomes a wife. But is the girl ready for sex yet or not? What is the appropriate age for having sex for the first time? This varies according to enviroment and traditions. In Yemen, girls were marrried off at nine, ten, eleven, eight or thirteen, while in other countries, they are married off at 16. Some countries have legislated laws forbidding having sex  before the girl is eighteen. The prophet Muhammad is the model we follow. He took Aisha to be his wife when she was six, but he had sex with her only when she was nine. He consummated the marriage by having sex with her for the first time, when she was nine. We consider the prophet Muhammad to be our model.     (LBC TV Libanon June 19 2008)

Muslims who believe in Quran hold the prophet Muhammad as their model and therefore, Islam that based on Quran teaches that a man can have a girl as the wife and with her can have sex for the first time when the girl is at nine. The practice of Islam about sex between a man and a girl fulfil the sign of pedophilia.

The Quran further exposes Muhammad's personal sexual attractions and addictions:

Quran Su 33: 50. O prophet! we have made lawful to thee thy wives to whom thou hast paid their dowers; and those whom thy right hand possesses out of the prisoners of war whom Allah has assigned to thee; and daughters of thy paternal uncles and aunts, and daughters of thy maternal uncles and aunts, who migrated from Mecca with thee; and any believing woman who dedicates her soul to the prophet if the prophet wishes to wed her;-- this only for thee, and not for the believers at large; we know what we have appointed for them as to their wives and the captives whom their right hands possess;-- in order that there should be no difficulty for thee. and Allah is oft-forgiving, most merciful.

Sura 33:50 indicates how Muhammad's life was uncontrollably ruled by sexual lusts and desires, and that he along had exclusive privileges in this area. According to the Quran, Muhammad had almost absolute and unlimited rights to take whoever he wanted to be his wife, but others did not have this right. From this, we can see how Muhammad's own desire for women overruled the previously written word of his god. The real Almighty God wouldn't have given this order, which would allow a prophet to take almost anyone he wanted to be his wife, even the wife of another. This verse from the Quran is a deception formed by evil spirits or by Muhammad, who wanted to carry out his own sexual lusts and desires.

I repeat, Islam emphasizes men's sexual desires towards women. The Quran only promises men, as a reward, sexual pleasures in paradise if that Muslim would fight against the heretics. That promise of sexual pleasure is comprised of 72 virgins awaiting in Heaven because of their willingness to practice terrorism against the heretics. What sort of god would offer pleasure in exchange for murder? Do you really understand what sort of god wishes to murder?

Polygamy

The Quran teaches that Muslims can have many wives. Islam is the religion that approves the polygamy.

Quran brings forth that Muslim can't be fair and just towards their wives and can't treat fairly all wives, even if it is his ardent desire. It is true that polygamy can't treat all wives equally, because someone always suffers, one way or another, and is not paid attention as should be. When a man has several wives, it is the indication that he is a slave of uncontrollable sex lusts. He needs all the time sex with several women. This kind of behavior is a sin and fornication according to the Bible.

Some people say that the Bible teaches polygamy, and therefore, it should be allowed in today's society. The Bible doesn't teach polygamy, but a permanent relationship (marriage) between a man and a woman. Teaching of the Bible is the life-long relationship between a man and a woman.

Mark 10:
6 But from the beginning of the creation God made them male and female.
7 For this cause shall a man leave his father and mother, and cleave to his wife;
8 And they twain shall be one flesh: so then they are no more twain, but one flesh.
9 What therefore God hath joined together, let not man put asunder.

1 Cor 7:2 Nevertheless, to avoid fornication, let every man have his own wife, and let every woman have her own husband.

The Lord Jesus taught that from the beginning of the creation, the will of God has been the permanent relationship between a man and a woman. Apostle Paul teaches that avoiding of fornication every man must have one wife, and wife must have one husband. Bible's teaching is therefore, very clear that polygamy is contrary to God's will.

In the Bible before the time of the Old Covenant, inter alia, Abraham, Jacob, David and Solomon had many wives. Why did God allow this, even though He says in His word, that God's will is the relationship between one man and woman? The Bible doesn't tell the answer why He allowed the polygamy a certain time in history, even though He teaches in His word that the marriage is between one man and woman. In the era of the New Covenant is clearly valid the marriage between one man and woman.

I bring forth thoughts that could be possible reasons why God allowed the matter that is not according to His will. I'm not saying that the matter is, as I write, but that following matters could be possible reasons why God allowed the polygamy a certain time in history.

When a man chooses wrong matters, he has to face the unpleasant consequences of his deeds. Polygamy brings conflict, discord, envy, jealousy and inequality. I believe that God knew when He allowed polygamy to the Old Testament people that they drive themselves to the plight, but because the stubbornness of people, He allowed it to them. Polygamy is wrong, but if someone wants to break himself stubbornly, so God allowed it in the time of Old Testament. People of the Old Testament got into trouble and suffered consequences of their choice. Wives clashed jealously, and the man tried to appease all of his wives, even though it was impossible. The polygamous family lives in the middle of conflicts, disputes and tensions. A man had to reap the consequences of his actions. God wanted to save people from these tensions and conflicts, but a man as the slave of sin chooses wrongly and trespasses against himself and other people.

God has said that divorce should not be taken, but He has made exceptions, such as adultery against the spouse. At this point, God has made an exception and allowed the matter that is not according to His will. For the reason of sin and disgusting adultery, He allowed an exception to divorce, because God loves people, and does not want people to suffer and be unhappy. I believe that approving of the polygamy is same features than the divorce case mentioned above.

God in His grace, allowed polygamy in a certain situation because of sin and the weakness of the flesh of man. God certainly saw how stubborn the people were and how they trespassed, and would trespass against Him.

God may work as a small child's parents work, who raise their children. When a child is small, so he can make all kinds of things, which is not correct, and can hurt and damage him. Parents can't say all the time, that you did wrong, but they give child time to grow and learn from the mistakes, which he has done. In such an environment would be distressing to grow, where all the time someone draws attention to wrong choices and actions. As the child grows, he learns from his mistakes and wants to reject the wrong thoughts and deeds. Maybe God thought the same way, and saw that the man is not able to do in all things the will of God. That is why God chose things that were destructive to man, and those commandments were clear and unconditional. But there were some things that were wrong, but people didn't have the strength to resist them, and so God allowed them to do something that is not according to His will, and is less harmful to them.

Similarly, the parents works, they set certain limits on small children, but allow the child to make certain mistakes because he has not the ability and understanding to act like an adult.

However, I believe. The question was that Old Testament people didn't have the power of the Holy Spirit and experience of the regeneration. That's why God allowed certain things to happen, even though they were not God's will. I believe that this was the main reason for the authorization of polygamy in the Old Testament people.

Old Testament people had no power to resist sin in their heart, because God's law had been written in stone, not the heart. During the New Covenant God's law (teaching) has given as the power in the Holy Spirit, that he can resist sin and learn to live in the faith according to the will of God. Perhaps it is so that God suffered weakness of the flesh of man to resist sin, and He allowed some things to them, which were not God's will.

Acts 17:
30 And the times of this ignorance God winked at; but now commandeth all men every where to repent:
31 Because he hath appointed a day, in the which he will judge the world in righteousness by that man whom he hath ordained; whereof he hath given assurance unto all men, in that he hath raised him from the dead.

Teaching of the Bible seems to support this idea, because the Bible says, referring to the time before the first coming of Jesus into the earth that the times of this ignorance God winked at. At the same time, however, the Bible teaches that it is now the time of the New Covenant. God makes it known that all people everywhere must repent and believe in the Lord Jesus Christ and live by the power of the Holy Spirit according to God's will.

We are living now in the time of the New Covenant, where God doesn't allow polygamy anymore, but it is clear sin, which the Lord Jesus and Paul's teachings prove to us. God has given to Jesus' disciples the power of the Holy Spirit, by which they can resist sin and to live according to God's will.

You can read the whole article in here: Differences Quran and Bible