Musnad Ahmad 30:1875

'Ali ibn 'Abdullah narrated to us, he said: Mu'adh ibn Hisham narrated to us, he said: My father narrated to me, from Qatadah, from Khallas ibn 'Amr, from Abu Rafi'—meaning the goldsmith—from Abu Hurairah, that the Prophet of Allah, peace and blessings of Allah be upon him, said: "The believer has two wives, the marrow of whose shins he sees from beneath their garments."