Jami` at-Tirmidhi Book 25, Hadith 75
From 'Aishah that the Messenger of Allah (ﷺ) said: "When one of you eats food, then let him say: 'Bismillah.' If he forgets in the beginning, then let him say: 'Bismillah Fi Awwalihi Wa Akhirih (In the Name of Allah in its beginning and its end.)"
That he entered upon the Messenger of Allah (ﷺ) while he has some food. He said: "Sit down O my son! Mention Allah's Name and eat with your right hand, and eat what is nearest to you."
It has been reported from Hisham bin 'Urwah, from Abu Wajzah As-Sa'idi, from a man from Muzainah, from 'Umar bin Abu Salamah. The Companions of Hisham bin 'Urwah differed in reporting this Hadith. Abu Wajzah As-Sa'di's name is Yazid bin 'Ubaid.
"The Prophet (ﷺ) was eating food with six of his Companions. A Bedouin came and ate it in two mouthfuls. So the Messenger of Allah (ﷺ) said: "As for him, had he mentioned (Allah's Name), it would have been enough for all of you."
This Hadith is Hasan Sahih. Umm Kulthum is the daughter of Muhammad bin Abi Bakr As-Siddiq, may Allah be pleased with them.