And the reason why the above was important

#2375. A father and a paternal grandfather can marry for their child who has not yet reached puberty, or was an insane when reaching puberty; and after that child reached puberty, or the insane became sane, he cannot cancel the marriage that was done for him if it did not involve a mischief against him and can cancel it if a mischief was involved.

#2410. If a person contracts for himself a girl who has not reached puberty and before she finishes her ninth year enters the girl he must never have intercourse with her in case he causes her path of urine and menses or that of menses and stool to become one.

#2459. It is recommended that one hurries in giving husband to a daughter who has attained puberty, meaning that she is of the age of religious accountability. His Holiness, Sadegh, salutations to him, bade that it is one of a man's good fortunes that his daughter does not see menses in his own house.

From A Clarification of Questions by Ayatollah Sayyed Ruhollah Mousavi Khomeini, the 1st Supreme Leader of Iran, who married a 10-year-old girl at 27.