All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
Dear brother, what your friend is saying is nothing but an enormous lie and slander. He is talking about the marriage of the Prophet with Zaynab bint Jahsh who was the wife of Zayd ibn Haarithah who was known as Zayd ibn Muhammad because the Prophet had adopted him.
In fact, an important legislation was passed through this marriage whereby the tradition of adopting children was annulled. Zayd used to come to the Prophet and make complaints about his wife Zaynab . Allaah The Almighty made it known to the Prophet that Zayd would divorce his wife Zaynab and that she would become his (the Prophet's) wife. Nevertheless, the Prophet kept replying to Zayd's complaints by saying: "Keep your wife to yourself and fear Allaah". Despite this, Zayd decided finally to divorce Zaynab . After Zayd divorced her, the Prophet married her to annul the tradition of adoption that was hitherto considered at par with kinship by blood.
As for the large number of marriages the Prophet contracted, they are not surprising. What is astonishing is the fact that some people deny the right of the Prophet to marry twelve women who were all divorced or widowed except 'Aa'ishah, who was the only virgin among them. Here I would like to quote a story of an exchange that occurred between a Muslim scholar and an Orientalist. The man said, "How do you respect a man who married nine women?" The scholar did not explain immediately the reasons for the Prophet's marriages because he knew that the Orientalist was blinded by his extremist views about Islam. So he replied by asking another question, "Do you respect the prophets of the Torah?" The man said, "Yes." The scholar said, "Do you respect Prophet Daawood (David) ?" The man said, "Yes." The scholar asked, "Do you respect Prophet Sulaymaan (Solomon) ?" The man said, "Yes." The scholar said, "Prophet Daawood (David) had ninety nine wives to whom he added another wife so he had a hundred wives. Prophet Sulaymaan (Solomon) had three hundred wives and seven hundred women slaves.” At this, the Orientalist was silenced and he did not utter any word.
In fact, the life of the Prophet went through three stages as far as his marriages are concerned:
First: the pre-marriage period
It is well known that the Prophet grew up in the Arab peninsula, which is a very hot region. In this region adolescents and youngsters reach the age of puberty very early. Their emotional feelings and sexual desires are usually very strong. So they get married at early ages or become perverted, going astray because of their desires and pleasures. Although the Prophet grew up in such an environment and stayed until the age of twenty-five without getting married, he never deviated from the right way. This was recognized by the Orientalist Moller, who said, "All sources concord that the Prophet – while young — was marked by calmness, gentleness and by keeping away from sins that the Quraysh used to commit ".
Second: the phase of monogamy
Before his marriage, the Prophet was employed as a trader by a wealthy, honorable and noble lady, Khadeejah . She was fifteen years older than him . She noticed his honesty, chastity and good qualities and sent a proposal of marriage. He married her and had all his children from her except his son Ibraaheem, whose mother was Maariyah an Egyptian slave girl. He stayed with his wife Khadeejah until she died. He was over fifty years old then. He never thought of marrying any other woman while married to Khadeejah even although polygamy was a common practice during those days. Even after her death, he stayed faithful to her and used to remember her often and spoke of her good character, to the extent that some of his other wives became jealous when he spoke of her.
Third: the phase of polygamy
When Khadeejah died, the Prophet became underwent a period of great sadness and sorrow. Due to this great sadness, his Companions called this year "The Year of Sorrow". When they noticed his grief, they sympathized with him and sent Khawlah bint Hakeem, the wife of ‘Abdullaah ibn Madh'oon both, to urge him to marry. However, he said: "A wife after Khadeejah?" She said, "I suggest 'Aa'ishah the daughter of Abu Bakr, the person you like the most."
He said: "But she is young", at which Khawlah said that she would mature in time.
When the Prophet expressed his worry about who would look after his daughters until 'Aa'ishah attained maturity, Khawlah suggested Sawdah bint Zam'ah . She was the widow of a Companion called Sakraan who was left with his family who were all polytheists, after his death upon returning from the first Hijrah (emigration). The Prophet married Sawdah bint Zam'ah and when the people heard about this marriage, they all agreed that he did so pitying her, in order to protect her from being driven away from Islam by Sakraan's family, as she was old and not beautiful. He stayed with her as his only wife for 4 years until 'Aa'ishah reached the age of maturity. This is sound evidence that the polygamy he practiced after the age of fifty-four was not for pleasure or sexual desire. It was rather for humanitarian, political and legislative reasons.
As for Hafsah, the daughter of ‘Umar both, her husband Khunays was killed as a martyr in the Battle of Badr, when she was only eighteen. So her father proposed her for marriage to Abu Bakr who did not reply to him. Then he proposed her to ‘Uthmaan whose wife, the daughter of the Prophet had just died. ‘Uthmaan did not reply to him either.
‘Umar was extremely unhappy with his companions' replies. So he went to the Prophet and complained to him about what happened. The Prophet replied with an answer that both pleased ‘Umar and healed his wounds, he said: "Hafsah will be married to a person who is better for her than ‘Uthmaan. And ‘Uthmaan will marry someone better for him than Hafsah." Then the Prophet himself married Hafsah .
Thus, the fact that ‘Umar proposed his daughter to his companions shows how important it was for the Muslims to marry the widows of the martyrs in order to console them and protect their chastity. As for Zaynab bint Khuzaymah Al-Hilaaliyyah, she was the widow of ‘Ubaydah ibn Al-Haarith, the cousin of the Prophet .
Umm Salamah, the Prophet's other wife was the wife of ‘Abdullaah ibn ‘Abdul Asad, the son of the paternal aunt of the Prophet . ‘Abdullaah was killed after the Battle of Uhud. Both Abu Bakr and ‘Umar proposed to marry her but she turned down their offers. When the Prophet proposed to marry her, she excused herself, saying that she was old, jealous and had many children. The Prophet said to her: "As for your age I am older than you are, as for your jealousy, Allaah will take it away, as for your children, they are for Allaah and his Messenger." Then the marriage took place.
This is yet another reason proving that he was not driven in his marriages by desire or pleasure but rather for protecting the widows and their children. So, all his marriages were either consoling the women he married or for arousing the interest of their tribes in Islam. Had there been any place for lust, he would not have chosen to marry elderly women and widows. As a matter of fact, he did not marry but one virgin, 'Aa'ishah .
Allaah Knows best.