The following is an explanation given by Shaykh Yusuf
Estes, which deals with the issue of Prophet
Muhammad's marriage to Ummul Mu'mineen Aisha 
The concern about the marriage of the Prophet 
with Aisha has usually to do with the age of
Aisha at the time of her marriage. The
question usually asked here is 'Is it true that the
Prophet married Aisha when she was a
child? And if so, what does this mean and how do we
understand that about child brides in Islam?'
What we want to tell you before we begin is that
Islam is always about rights and limits. Never is it
permissible in Islam to take advantage of anybody
else. Allah 
clearly tells us that he does not
oppress and he hates those who oppress and he forbids
humans to oppress each other. So if you're imagining
some kind of oppression here, you can put your mind at
ease; this is not oppression.
Let us now investigate what were the conditions and
the customs and traditions of the people at the time
of the Prophet . The Arabs of the Arabian
Peninsula at that time used to marry a girl at any
age. There was no limit on it. Because it wasn't
about sexual intercourse or anything. It was about
establishing the right of marriage of a man getting
to marry a girl and marrying in to a family. It was
about tribalism and with little of any stipulation
that the girl had any say or any rights. As a matter
of fact, that was the last and the least of their
considerations.
Additionally, in those days it was considered a
shame on the family if they had a child that was a
girl born to them. So some of the men would take
these girls when they were born, in to the desert and
bury them alive. That was considered the manly thing
to do. And when a child was orphaned, lets say there
was a little girl whose father passed away, then a man
could come along and claim that I want to marry this
girl and take all the wealth that she was to inherit.
People would also take the wealth of boys and girls
and mix it with their own wealth and claim that they
were improving the condition for that child until they
got old enough to make decisions for themselves. And
obviously benefiting themselves with this mingling of
funds.
So, when Islam came (in stages). It came with the
thought that it is God who has authority over man. And
this was the Tawheed, the monotheism that was the
influential thought and teaching of Prophet Muhammad
. And here now it was he showing God's authority
to behave, especially in this idea of being married.
So there is a surah now in the Qur'an about women.
In this surah, dealing with issues related to
women, which is the fourth surah . You can go to
ayah 19 which says 'O you who believe. You cannot
inherit women against their will.' Meaning that you
cannot take from them their inheritance and meaning
also that you cannot marry them without their consent
and they have to be old enough for the age of consent.
This is very clear. A man could not marry a girl. He
can only marry a woman. A woman meaning she's old
enough to have children, and mature enough to make
these kind of decisions.
Now let us turn to the subject at hand, which is
the age of Aisha . Only Aisha herself
is telling us about this. She is telling us in her own
words what her age was when her mother came to her and
she (Aisha ) was playing outside, and her mother
asks her to come in the house. She was six years old.
Her mother takes her in to the house to see her father.
Her father is there, offering her hand in marriage now
to Prophet Muhammad . And this was a custom and
tradition in their society. So it was definitely within
the limits of the society they live in and it was
approved of, but look at this. It wasn't accepted by
Prophet Muhammad .
How do we know this? Because if you continue
reading, we find that she went back outside and
continued playing. And this is to indicate what? That
although this is very much appreciated, at least in
intention, yet the girl's not old enough and she must
be the one to decide. Thats why you find another
Hadeeth in the same book of Bukhari that mentions a
different age. So you may wonder, is it 6 years old or
is it 9 years old? Maybe they turned the number upside
down?! But that's not possible in Arabic :). In fact
a similar incident happens in another place. Again her
mother is taking her inside with her father offering
her hand in marriage to the Prophet . At this
time she's older and in a position to make this
decision. But then again they did not have any marriage
until she gave consent.
The second part is that even when she got married to
the Prophet , she didn't go live with him until
she was old enough to have children. That's also a
condition and an understanding in Islam. And even then,
he (the Prophet ) took his time with her. She said
herself, that they used to run, play, and enjoy being
together. And she talks about growing up with him and
also the mutual love and respect for each other. In her
whole life she never mentioned any disparaging remarks
against her husband. It was only the most glowing of
reports that comes from her about Prophet Muhammad
. Although he died when she was still a young
lady, she continued in her life with full respect and
honor. She never remarried.
She also became one of the best scholars in the
area about telling us of women's needs and women's
conditions and things that Islam is providing for
women. We know a lot about this from Aisha .
Additionally, I would ask you to consider how much
he loved her. When he was dying, he wanted to be with
her and he made a point to be there. And she would take
care of him at this time. And he passed away with his
head in her lap. Now this shows a great love between
both of them. Yet she didn't wail, or cry, or tear at
her dress. Instead she understood that he was going to
his lord. She also understood throughout the rest of
her life that she also would go to her lord and that
they would be together again in paradise living happily
ever after.
I'd like you now to contrast this story that I've
just told you with the story of Romeo and Juliet, which
we usually associate with Valentine's day and true love
and young love. But in reality, the story that
Shakespeare presents to us is no match for the
beautiful story that I've just told you. Because those
two of them (Romeo and Juliet), and they were children,
perhaps 12-14 years old. They were going against the
wishes of their parents and sneaking behind their back
and they were not married. It was just an affair that
they were having. And then one committed suicide and
then the other followed. So this is the tragic result
of the kind of love that is not acceptable in Islam.
There is not boyfriend-girlfriend relationship. And
there is certainly no sneaking behind the back of
parents. Everything in Islam is out in the open. And
everything is done by contract. And there is never any
sex before marriage.
So put it in perspective and understand that the
story (of the Prophet and Aisha ) is what
Shakespeare probably wishes he told instead of Romeo
and Juliet. I hope this explanation was in some way
able to put your mind at ease in relation to this
subject because Prophet Muhammad was sent as a
mercy to the whole of the mankind and jinn.
And Allah knows best.