From Wikipedia about polygamy of our beloved Prophet Pbuh and polygamy in Islam
Main article: Polygamy in Islam
In Islam, polygamy is allowed for men (making it polygyny), with the specific limitation that they can only have up to four wives at any one time. The Qur'an also clearly states that men who choose this route must deal with their wives as fairly as possible, doing everything that they can to spend equal amounts of time and money on each one of them. If the husband cannot deal with his wives fairly, one is enough. Women on the other hand, are only allowed the one husband (no polyandry), although they are allowed to remarry after a divorce, unlike many other cultures further east. Although many Muslim countries still retain traditional Islamic law which permits polygamy, secular elements within some Muslim societies challenge its acceptability. Polygamy is prohibited by law in some Muslim countries that have not adopted Islamic law for marital regulations, such as Azerbaijan, Bosnia-Herzegovina, Tunisia and Turkey.
Historically,polygyny was considered an act of pride and power, because a man announced openly in his tribe that he is responsible for taking care of another family. In this term it has it roots on pride, courage and gallantry to take lawful responsibilities for other people (especially widowed women).
Polygamy, and laws concerning polygamy, differ greatly throughout the Islamic world and form a very complex and diverse background from nation to nation. Whereas in some Muslim countries it may be fairly common, in most others it is often rare or non-existent. According to traditional Islamic law, a man may take up to four wives, and each of those wives must have her own property, assets, and dowry. Usually the wives have little to no contact with each other and lead separate, individual lives in their own houses, and sometimes in different cities, though they all share the same husband. Prophet Muhammad, who had a monogamous marriage with Khadija for twenty five years till her death, married many of his wives because they were war widows who were left with nothing and took care of them (Muhammad had 9 wives, see Muhammad's wives). Thus, polygamy is an exception rather than the rule and is traditionally restricted to men who can manage things, and in some countries it is illegal for a man to marry multiple wives if he is unable to afford to take care of each of them properly
( يا أيها الناس اتقوا ربكم الذي خلقكم من نفس واحدة )
ثم وصف تعالى ذكره نفسه بأنه المتوحد بخلق جميع الأنام من شخص واحد ، معرفا عباده كيف كان مبتدأ إنشائه ذلك من النفس الواحدة ، ومنبههم بذلك على أن جميعهم بنو رجل واحد وأم واحدة وأن بعضهم من بعض ، وأن حق بعضهم على بعض واجب وجوب حق الأخ على أخيه ، لاجتماعهم في النسب إلى أب واحد وأم واحدة وأن الذي يلزمهم من رعاية بعضهم حق بعض ، وإن بعد التلاقي في النسب إلى الأب الجامع بينهم ، مثل الذي يلزمهم من ذلك في النسب الأدنى وعاطفا بذلك بعضهم على بعض ، ليتناصفوا ولا يتظالموا ، وليبذل القوي من نفسه للضعيف حقه بالمعروف على ما ألزمه الله له (تفسير الطبرى)