Sahih al-Bukhari 6960

'Ubaydullah said, "Nafi' related to me that 'Abdullah said that the Messenger of Allah, may Allah bless him and grant him peace, forbade the shighar. I asked Nafi', 'What is the shighar?' He answered, 'It is when a man marries a man�s daughter who then, in turn, marries his daughter without any dowry being exchanged between them, or that a man marries the sister of a man who then marries his sister without any dowry being dowry exchanged between them." Some people said, "If someone employs a stratagem so that he marries by means of shighar, the marriage is then valid but the stipulation is void." He said about the mu'ta [temporary marriage], "The marriage is invalid and the stipulation is void." One of them said, "Both the mu'ta and the shighar are permitted, but the precondition is void."