Several places in The Bible God says that one man is to marry one woman. The first place is in Genesis, around the third chapter I believe. To do anything else is to invite trouble like jealousy etc. You can see some of the problems inherent in polygamy in the relationship Jacob had with Rachel and Leah among others.
A:
Christianity prohibits polygamy on historical and ethical grounds.
The historical reason is no doubt the less important. Whereas the Jews still permitted polygamy in the first century, when Christianity arose, the dominant pagans saw polygamy as immoral, and Rome itself regarded it as a crime. Christianity spread through the gentile regions of the empire and was therefore influenced by the moral standards of the empire.
The ethical and moral reasons can be more nuanced. Polygamy almost always creates women as second-class, with men dominating their harems , no matter how publicly they claim to treat their women well. If women were equally permitted to have multiple husbands (polyandry), this would be some evidence of equality, but they almost never are.
Another ethical reason is that nature creates equal numbers of boys and girls (actually slightly more boys than girls). Every man who is able to take more than one wife must mean another man who remains unmarried. Of course, women can be rationed by a bride-price or dowry, so that only the wealthy can afford wives: this is yet another ethical concern.
It is not a defence of polygamy to say that polygamy allows a man to take a widow or destitute woman as a second wife, since monogamous societies solve this very well by treating women as equals. Widows and potentially destitute women can marry single or widowed men.
Since polygamy means that some men must remain unmarried, these unfortunate men face pressure to become homosexual, even when that is not their natural inclination - yet religions that espouse polygamy are loudest in condemning homosexuality. Another potential outcome is sexual assault of women, by young men with little chance of fulfilling their urges through marriage.
Polygamy, Bigamy, and sometimes civil unions
By and large modern Judaism and modern Christianity do not promote polygamy, but historically both did. In either case, the two religions are similar in this respect.
Polygamy is not acceptable in Christianity. In 285 CE, the Roman Empire created historical bigamy laws for newly forming Christian countries.
Many leaders have allowed Christianity and many have prohibited it.
No, the Romney's in Mexico no longer practice polygamy, and have not for about 100 years. They are members of the Church of Jesus Christ of Latter-day Saints, which has prohibited the practice.
Nowadays they don't practice but their holy books some prophets are polygamist
It is a form of gambling which is prohibited in most religions such as Christianity.
Henry Bitakaramire has written: 'Traditional and Christian marriage' -- subject(s): Christianity, Marriage, Marriage customs and rites, Polygamy, Religious aspects, Religious aspects of Marriage, Religious aspects of Polygamy
N. Engelbert Kofon has written: 'Polygyny in pre-Christian Bafut and new moral theological perspectives' -- subject(s): Bafut (African people), Christianity, Polygamy, Religion, Religious aspects, Religious aspects of Polygamy
Only if they don't know each other...(just kidding). Polygamy, while not prohibited by Federal Law, is against the law in each of the individual United States.
The Mormon Church banned polygamy in 1890, and Utah was admitted as a state in 1896. This wasn't the only condition to Utah's statehood, but it was a factor.
The government allows several specific churches, but conversion from Islam to another religion is prohibited.