Grand Ayatollah as-Sistani gave the following fatwa on the permissibility of Muslims marrying and having sex with girls below the age of puberty.
Apparently, it is permissible for a Muslim to marry and have sex with a girl below the age of puberty (i.e. non-baligh) as long as she has passed the age of nine. She is still not-haram to him after she attains puberty. But if he has damaged her sexual organs by having sex with her, he is advised to divorce her. What kindness.
- If a person contracts Nikah with a non-baligh girl, it is haraam to have sexual intercourse before she has completed her nine years. But if he commits sexual intercourse with her, she will not be haraam for him when she becomes baligh, even if she may have suffered Ifza (which has been described in rule 2389), though as a precaution, he should divorce her.
This is what Ifza means:
Opening. State of a woman that her urinary and menstrual tract or her menstrual passage and rectum, or all three of them have become one.
The nine year limit is in consideration to Muhammad’s marriage to Aisha as he also married and had sex with a pre-pubertal girl of the age of nine.
Please note the morality and kindness of having sex and damaging the sexual organs of a pre-pubertal girl of nine. Please also note the morality of divorcing her once her sexual organs have been damaged and casting her away like trash.