Musnad Ahmad 30:2637

Waki’ narrated to us, from Ibn Abi Dhi’b, from Salih, the freed slave of al-Taw’amah, from Abu Hurairah, that when the Messenger of Allah (peace and blessings of Allah be upon him) performed Hajj with his wives, he said: "It is only this Hajj, then [remain] upon the backs of the mats."