From Sahih Bukhari (Hadith 5450):
Narrated Anas:My mother, Um Sulaim, took a Mudd of barley grain, ground it and made porridge from it, and pressed (over it), a butter skin she had with her. Then she sent me to the Prophet, and I reached him while he was sitting with his companions. I invited him, whereupon he said, "And those who are with me?' I returned and said, "He says, 'And those who are with me?" Abu Talha went out to him and said, "O Allah's Messenger (ﷺ)! It is just a meal prepared by Um Sulaim." The Prophet (ﷺ) entered and the food was brought to him. He said, "Let ten persons enter upon me." Those ten entered and ate their fill. Again he said, 'Let ten (more) enter upon me." Those ten entered and ate their fill. Then he said, "Let ten (more) enter upon me." He called forty persons in all Then Allah's Messenger (ﷺ) ate and got up. I started looking (at the food) to see if it decreased or not
Reference: Bukhari 5450