the prophet pbuh married khadijah when he was twenty-five years of age and she was forty. it was after he had traveled to syriaon a business trip for her with her servant, maysarah, who was much impressed by him and his integrity. upon their return, he informed her of what he had observed. she sent a proposal of marriage to him and he married her.
khadijah died three years before the prophet's hijrah (emigration from makkah). he had been with her for twenty-five years, and she was his only wife until she died at the age of sixty-five. the prophet pbuh was about fifty at that time. after that he married a number of women for various noble causes and aims. this refutes what is claimed by some orientalists and opponents that the prophet pbuh was driven by lust and was seeking pleasure. how could this be when he had remained with one wife, fifteen years his senior, without marrying another until her death and after the age of youthful desires had passed? was his sexuality latent all those years and then suddenly appeared when he reached the age of fifty? this is something no intelligent person will accept.
many western scholars and intellectuals have themselves found this claim to be ridiculous. the italian researcher, dr. laura vaghlieri said, "during his years of youth when sexual desire is greatest and in spite of having lived in a society such as that of the arabs before islam, where marriage as a social institution was almost non-existent and where plural wives was the rule and divorce extremely easy, muhammad pbuh did not marry but one wife. she was khadijah, who was much older than himself. he remained her loyal, loving husband for twenty-five years and never married a second time or more than one except after khadijah died and after he had reached the age of fifty."
all of his subsequent marriages had a social or political motivation. they were based on the intent to honour women who were known to be righteous or to establish ties of kinship with some other tribes in order to facilitate the spread of islam. with the exception of `a'ishah, muhammad pbuh did not marry any virgin or young woman. can this be seen as lust?
given that he was a man and not a god, it is also possible that he married out of desire for a son, as those he had from khadijah had died.
without much source of income, he pbuh took on the responsibilities and burdens of a large family. but he always observed perfectly equal treatment for all his wives, never once claiming the right to separate from any of them.
his conduct was in accordance with the tradition of the former prophets; moses and others, whom people have never criticized for plural marriages. could this be because we do not know the details of their personal lives while we do know everything about the family life of prophet muhammad pbuh ?
after the death of khadijah the prophet pbuh married sawdah bint zam`ah, then `a'ishah bint abi bakr as-siddiq, and she was the only virgin he married. then he married hafsah bint `umar ibn al-khattab and then zaynab bint khuzaymah ibn al-harith. and he married umm salamah, whose name was hind bint abi umayyah, and zaynab bint jahsh and juwairiah bint al-harith and umm habibah, whose name was ramlah bint abi sufyan. and after the conquest of khaybar he married safiyyah bint huyayy and then maymunah bint al-harith; and she was the last woman he married.
from the book they say about islam by dr. imad ad-deen khalil, pp. 120-121.