四分律比丘含注戒本 2.115

2.115

The Buddha was in Śrāvastī. A householder invited the Saṃgha. The group of seventeen bhikṣus took the Saṃgha's sitting mats, spread them in the open, and walked up and down, waiting for the mealtime to arrive. Without packing them away, they went to eat; [the mats] were soiled by wind and dust, and damaged and defiled by insects and birds. They reported the fault to the Buddha. Having rebuked them, he laid down the precept.