I asked Saad bin Abu Waqqas about mutah, and he said, "We practiced it while this man was still a disbeliever residing in the dwellings of Mecca," meaning Muawiya.
حدثنا يحيى بن سعيد أنبأنا سليمان يعني التيمي
سألت سعد بن أبي وقاص عن المتعة قال فعلناها وهذا كافر بالعرش يعني معاوية
Its chain of transmission is sahih. Ghunaym is Ibn Qays al-Mazini al-Kabi, who lived during the time of the Messenger of Allah ﷺ but did not see him, and he came as a delegate to Umar. He is trustworthy, from the first generation of the people of Basra. Here, "mutah" refers to the mutah of Hajj, as explained by the previous hadith 1503.