I asked Sa'd b. Abu Waqqas (Allah be pleased with him) about Mut'a, whereupon he said: We did that, and it was the day when he was an unbeliever living in (one of the) houses of Mecca.
Reference: Sahih Muslim 1225 a In-book : Book 15, Hadith 178 USC-MSA web (English) : Book 7, Hadith 2821 (deprecated)
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