Sahih Bukhari

Narrated 'Abdullah: Nafi narrated to me that 'Abdullah said that Allah's Messenger (ﷺ) forbade the Shighar. I asked Nafi', ""What is the Shighar?"" He said, ""It is to marry the daughter of a man and marry one's daughter to that man (at the same time) without Mahr (in both cases); or to marry the sister of a man and marry one's own sister to that man without Mahr."" Some people said, ""If one, by a trick, marries on the basis of Shighar, the marriage is valid but its condition is illegal."" The same scholar said regarding Al-Mut'a, ""The marriage is invalid and its condition is illegal."" Some others said, ""The Mut'a and the Shighar are permissible but the condition is illegal