I will be addressing two issues:
What is the prescribed marriage age in Islam for a woman?
What age did Prophet Muhammed marry Ayesha?
- What is the prescribed marriage age in Islam for a woman?
And try orphans (as regards their intelligence) until they reach the age of marriage; ..... - 4:6
There is a term in the Quran that presupposes there is an age of marriage. What is this age? Scholars agree that it is puberty.
The Prophet himself alludes to this with the following quote:
The Noble Prophet (S) has said: "Virgin girls are like fruits on trees. If not plucked in time, the sun will rot them and the wind will disperse them. When girls reach maturity and their sexual instincts arise, like that of women, their only remedy is marriage. If they aren't married, they are prone to moral corruption. It is because they are human beings and human beings are prone to making mistakes."
Here we can see that the age of marriage is when sexual instincts arise, and that is when puberty has occurred. And in fact as we see the prophet cautions against waiting too long to marry your post-pubesant daughters off because human nature is prone to sin (such as fornication).
- What age did Prophet Mohammed marry Ayesha?
There is one Hadith that seems to assert Prophet Muhammed married Ayesha, the daughtar of his good companion, at the age of 9. This has been repeated in western media by those that wish to slander Islam and discredit its leader. The intentions behind these assertions is character assassination.
Regardless, it has been proven by scholars that if we were to guess Ayesha's age of marriage to Prophet Muhammed, it is likely 18 or 19 years old. This is broken down with proofs from the following article:
https://www.scribd.com/document/7250931/Truth-About-the-Age-of-Hazrat-Ayesha-s-Age