Musnad Ahmad 304:9

Hassan ibn Musa narrated to us, he said: Ibn Lahi'ah narrated to us, Abu al-Aswad narrated to us, from Abd al-Rahman ibn Sa'd al-Muq'ad, from Umar ibn Abi Salamah, who said: Food was brought near to the Messenger of Allah, may Allah bless him and grant him peace. He said to his companions: "Mention the name of Allah, and let every man eat from what is next to him."