Musnad Abu Ya'la al-Mawsili 6:117

Abu Khaythama narrated to us, Uthman ibn Umar narrated to us, Malik narrated to us, from al-Zuhri, from Muhammad ibn Abdullah ibn Nawfal, that he heard Sa’d ibn Malik and al-Dahhak ibn Qays in the year Mu’awiyah performed Hajj, and they were mentioning the *Tamattu’* (combining) of the Umrah with the Hajj. Al-Dahhak said, "No one does that except one who is ignorant of the command of Allah." Sa’d said, "How evil is what you have said, O son of my brother!" Al-Dahhak said, "Umar forbade it." Sa’d said, "The Messenger of Allah, peace and blessings of Allah be upon him, performed it, and we performed it with him."