1. Equal treatment of all the wives
2. Preserving the purity and feeling of family life, so that it does not become the cause of disruption in family affairs
3. The number of wives does not exceed four
If you look at point number one (Equal treatment of all the wives), we will realize as to how hard that task is, to accomplish. Let’s see what the Qur’an has to say about polygamy: “And if you fear that you cannot act equitably towards orphans, then marry such women as seem good to you, two and three and four; but if you fear that you will not do justice (between them), then (marry) only one or what your right hands possess; this is more proper, that you may not deviate from the right course.” (4:3)
As mentioned earlier, that polygamy existed prior to Islam, but it existed with no limitations or restrictions. It was Islam which has restricted it as it was used and abused a lot by the wealthy people, rulers etc. that were not just at all. If a man lacks that special spirit and strength of treating more than one wife equally, he is not allowed to take more than one wife.
At the end, the best and the most satisfactory form of marriage is naturally monogamy, and therefore men should avail themselves of the permission of polygamy only in exceptional circumstances..