"The Prophet wrote the (marriage contract) with 'Aisha while she was six years old and consummated his marriage with her while she was nine years old and she remained with him for nine years (i.e. till his death)." -- Bukhari 7.62.88

Muslims take this seriously and imitate Muhammad in this. Article 1041 of the Civil Code of the Islamic Republic of Iran states that girls can be engaged before the age of nine, and married at nine: "Marriage before puberty (nine full lunar years for girls) is prohibited. Marriage contracted before reaching puberty with the permission of the guardian is valid provided that the interests of the ward are duly observed."

The Ayatollah Khomeini... http://www.jihadwatch.org/2012/11/saudi-arabia-5000-child-brides-under-a...