Musannaf Ibn Abi Shayba 9:1169

17072. Ubaydah narrated to us, from Ubayd Allah, from Nafi’, from Ibn Umar, that he was asked about *mut’ah* (temporary marriage), and he said: "It is forbidden." It was said to him: "Indeed, Ibn Abbas gives a legal opinion (fatwa) permitting it." He replied: "Why did he not do so during the time of Umar?"