Samyutta Nikaya I. 81-2
Once when the Buddha was living at Savatthi, King Pasenadi of Kosala ate a whole bucketful of food . The Buddha, discerning that King Pasenadi was engorged and panting, took the occasion to utter this verse: "When a person is constantly mindful, and knows when enough food has been taken, all their afflictions become more slender, they age more gradually, protecting their lives." Now at that time the brahman youth Sudassana was standing nearby, and King Pasenadi of Kosala addressed him: "Come now, my dear Sudassana, and having thoroughly mastered this verse in the presence of the Buddha, recite it whenever food is brought to me. Then King Pasenadi of Kosala gradually settled down to [eating] no more than a cup-full of rice. At a later time, when his body had become quite slim, King Pasenadi [said]: "Indeed the Buddha has shown me compassion in two different ways: For my welfare right here and now, and also for in the future."