Musnad Abu Ya'la al-Mawsili 209:115

Abu Khaythama informed us, [he said] Isma'il ibn Ibrahim narrated to us, from Muhammad ibn Ishaq, from 'Abdullah ibn Rafi', from Umm Salamah, she said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "If dinner is served and the prayer is [also] present, then begin with the dinner."