四分律比丘含注戒本 2.329

2.329

The Buddha was in Śrāvastī and taught the practice of one meal. Among the five kinds of food, they were made fully satisfied. Later, when they were still gaunt and weary, the Buddha said: 'I allow those attending the sick to also eat the leftover food of the sick person.' He also permitted 'performing the procedure for leftover food'. Some who were gluttonous did not know the procedure of eating, and on that account he formulated this precept.