"...Muhammad married a child. The example of Muhammad, "a beautiful pattern of conduct" according to Qur'an 33:21, cannot be set aside, or standards he set "updated," lest one imply Muhammad made a mistake. That would not only insult Muhammad (things seem to become flammable when that happens) but go against the Qur'an's endorsement of him, and therefore Allah's."
That is why child marriage persists in the Islamic world, from Nigeria to Yemen to Indonesia:
"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