Sa'id al-Maqburi (may Allah have mercy on him) narrates that Sayyiduna Ibn Abbas (may Allah be pleased with them both) and Urwah bin al-Zubayr (may Allah have mercy on him) differed about mut'ah. Urwah said: It is fornication. Sayyiduna Ibn Abbas (may Allah be pleased with them both) said: O Urayyah, what do you know? Just then Sayyiduna Salamah bin al-Akwa' (may Allah be pleased with him) passed by them, and Sayyiduna Ibn Abbas (may Allah be pleased with them both) asked him. He said: The Messenger of Allah (peace and blessings be upon him) took us far away (on a journey) for three months. I would go out with the army; when they halted, I halted too, and when they spent the evening, I did too. Then the Prophet (peace and blessings be upon him) said: "Whoever wishes may contract mut'ah with these women."
Hadith Referenceالمعجم الكبير للطبراني / باب السين / 6206