Nadya Labi checks out Iran's use of them:

In the Islamic Republic of Iran, sex outside of marriage is a crime, punishable by up to 100 lashes or, in the case of adultery, death by stoning. Yet the purpose of a temporary marriage is clear from its name in Arabicmut'a, pleasure. A man and a woman may contract a mut'a for a finite period of timefrom minutes to 99 years or moreand for a specific amount, mehr in Farsi, which the man owes the woman.

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