Sheikh Habib Al-Habib made the ruling Saturday in the Saudi city of Onaiza. Late last year, he rejected a petition to annul the marriage.
The case, which has drawn criticism from local and international rights groups, came to light in December when Al-Habib declined to annul the marriage on a legal technicality. His dismissal of the mother's petition sparked outrage and made headlines around the world.
The judge said the mother, who is separated from the girl's father, was not the legal guardian and therefore could not represent her daughter, the mother's lawyer, Abdullah al-Jutaili, said at the time.
The girl's husband pledged not to consummate the marriage until the girl reaches puberty, according to al-Jutaili, who added that the girl's father arranged the marriage to settle his debts with the man, who is considered "a close friend."