The Wives Of The Prophet
Religious And Legislative Purpose:
The Prophet (s) married Zainab b. Jahsh. The Arabs in the Era of Ignorance would prohibit a man from marrying the wife of his adopted son; they believed that the adopted son was like a man’s actual son in all aspects. The Prophet (s) married her, although she was previously the wife of his adopted son, Zaid b. Harithah. The Messenger of God (s) married her to abolish this belief. God, the Exalted, says:
(And when you said to him to whom Allah had shown favor and to whom you had shown a favor: keep your wife to yourself and be careful of (your duty to) Allah; and you concealed in your soul what Allah would bring to light, and you feared men, and Allah had a greater right that you should fear Him. But when Zaid had accomplished his want of her, We gave have her to you as a wife, so that there should be no difficulty for the believers in respect of the wives of their adopted sons, when they have accomplished their want of them; and Allah’s command shall be fulfilled..) (33:37)
Political Reasons And For The Spread Of Islam
To invite people to Islam, and to gain the favor of the Arab tribes:
The Messenger of God (s) married women from the largest and strongest Arab tribes. The Prophet (s) ordered his Companions to do this as well. The Prophet (s) said to Abdurrahmaan b. Auf:
‘If they obey you (i.e. accept Islam) then marry the daughter of the head of the tribe.’

Dr. Cahan said:
‘Some of the aspects of his life may seem confusing to us due to present day mentality. The Messenger is criticized due to his obsession of attaining worldly desires and his nine wives, whom he married after the death of his wife Khadeejah. It has been confirmed that most of these marriages were for political reasons, which were aimed to gain loyalty of some nobles, and tribes.’

Social Reasons:
The Prophet (s) married some of his Companions’ wives who had died, in battle or while on a mission to preach Islam. He married them even though they were older than him, and he did so to honor them and their husbands.

Veccia Vaglieri in her book ‘In Defense of Islam’ said:
‘Throughout the years of his youth, Muhammad (s) only married one woman, even though the sexuality of man is at its peak during this period. Although he lived in the society he lived in, wherein plural marriage was considered the general rule, and divorce was very easy – he only married one woman, although she was older than him. He was a faithful husband to her for twenty-five years, and did not marry another woman, except after her death. He at that time was fifty years old. He married each of his wives thereafter for a social or political purpose; such that he wanted to honor the pious women, or wanted the loyalty of certain tribes so that Islam would spread amongst them. All the wives Muhammad (s) married were not virgin, nor were they young or beautiful; except for A’ishah. So how can anyone claim that he was a lustful man? He was a man not a god. His wish to have a son may have also lead him to marry; for the children that he had from Khadeejah all died. Moreover, who undertook the financial responsibilities of his large family, without having large resources. He was just and fair towards them all and did not differentiate between them at all. He followed the practice of previous Prophets such as Moses, whom no one objected to their plural marriage. Is the reason why people object to the plural marriage of Muhammad (s) the fact that we know the minute details of his life, and know so little of the details of the lives of the Prophets before him?’

Thomas Carlyle said:
‘Mahomet himself, after all that can be said about him, was not a sensual man. We shall err widely if we consider this man as a common voluptuary, intent mainly on base enjoyments,–nay on enjoyments of any kind.’ ( ‘Heroes, Hero-Worship and the Heroic in History’ )