Muhammad bin Abdullah bin al-Harith bin Nawfal heard Sayyiduna Sa'd bin Abi Waqqas and al-Dahhak bin Qays (may Allah be pleased with them both) talking in the year of Sayyiduna Amir Mu'awiyah's (may Allah be pleased with him) Hajj, and they were discussing tamattu'. Al-Dahhak said: Only someone heedless of Allah's command would do this. Sayyiduna Sa'd (may Allah be pleased with him) said: O son of my brother, what an evil thing you have said! Al-Dahhak said: But Sayyiduna Umar bin al-Khattab (may Allah be pleased with him) used to forbid Hajj al-Tamattu'. Sayyiduna Sa'd (may Allah be pleased with him) said: The Messenger of Allah (peace and blessings be upon him) did it, and we did it along with him.
This is how it is in this narration: "The Messenger of Allah (peace and blessings be upon him) did it"; but in the established narrations of this hadith from Ghunaym bin Qays from Sayyiduna Sa'd (may Allah be pleased with him), the wording is "We did it", with no mention of the Prophet's (peace and blessings be upon him) doing it. And Allah knows best.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحج / 8854