Musnad Ahmad 32:1842

Sulayman ibn Dawud narrated to us, Isma'il narrated to us, he said: Humayd informed me, from Anas ibn Malik, who said: "The Prophet, may Allah bless him and grant him peace, stayed between Khaybar and Medina for three [days], consummating his marriage with Safiyyah bint Huyayy. I invited the Muslims to his wedding feast, and there was neither bread nor meat in it. He ordered the leather mats, and dates, dried yogurt (aqt), and ghee were cast upon them; that was his wedding feast. The Muslims said: '[Is she] one of the Mothers of the Believers, or [is she] what his right hand possesses?' They said: 'If he veils her, then she is one of the Mothers of the Believers, and if he does not veil her, then she is from what his right hand possesses.' When he departed, he prepared a seat for her behind him and extended the veil between her and the people."