Sahih al-Bukhari 5378
Narrated Wahb bin Kaisan Abi Nu'aim:
A meal was brought to Allah's Messenger (ﷺ) while his step-son, `Umar bin Abi Salama was with him. 
Allah's Messenger (ﷺ) said to him, "Mention the Name of Allah and eat of the dish what is nearer to you."
حَدَّثَنَا عَبْدُ اللَّهِ بْنُ يُوسُفَ، أَخْبَرَنَا مَالِكٌ، عَنْ وَهْبِ بْنِ كَيْسَانَ أَبِي نُعَيْمٍ، قَالَ أُتِيَ رَسُولُ اللَّهِ صلى الله عليه وسلم بِطَعَامٍ وَمَعَهُ رَبِيبُهُ عُمَرُ بْنُ أَبِي سَلَمَةَ فَقَالَ ‏
"‏ سَمِّ اللَّهَ، وَكُلْ مِمَّا يَلِيكَ ‏"‏‏.‏