Al-Rabi' bin Sabrah narrates from his father (Sayyiduna Sabrah, may Allah be pleased with him) that he said: I saw the Messenger of Allah (peace and blessings be upon him) standing between the door and the Corner, and he (peace and blessings be upon him) was saying: "O people, I had permitted you mut'ah marriage, but now Allah has made it unlawful until the Day of Resurrection. So whoever has such a woman with him, let him set her free, and do not take back anything of what you gave them."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب النكاح / 14154