He heard Saad bin Abu Waqqas and Dahhak bin Qays, during the year that Muawiya bin Abu Sufyan performed Hajj, discussing the practice of performing Umrah first and then Hajj.Dahhak said, "Only someone ignorant of Allah's command would do that."Saad replied, "What an evil thing you have said, son of my brother."Dahhak said, "But Umar bin Khattab forbade it."Saad answered, "The Messenger of Allah ﷺ did it, and we did it along with him."
أخبرنا قتيبة عن مالك عن ابن شهاب
أنه سمع سعد بن أبي وقاص والضحاك بن قيس عام حج معاوية بن أبي سفيان وهما يذكران التمتع بالعمرة إلى الحج فقال الضحاك لا يصنع ذلك إلا من جهل أمر الله تعالى فقال سعد بئسما قلت يا ابن أخي قال الضحاك فإن عمر بن الخطاب نهى عن ذلك قال سعد قد صنعها رسول الله ﷺ وصنعناها معه
Sourcing, its isnad is hasan. Tirmidhi narrated it in the Hajj chapter, section on what has been said about tamattu, hadith 823, from Qutayba with the same wording, and he said, "Sahih." It is also found in the Muwatta (Yahya's version), 1/344, and in Kubra, hadith 3714.Muhammad bin Abdullah is hasan al-hadith according to the more correct view. "He did it," meaning he permitted it and allowed it, as stated by Ibn Abdul-Barr in Tamhid, 8/360.