四分律比丘含注戒本 3.337

3.337

佛在舍衛。六群塔下坐食已，留食及草污地而去。以過白佛，因制不得坐食。又作塔、作房，若施池井，施食，眾僧集坐迮，聽塔下坐食，不應污地也。

The Buddha was in Śrāvastī. The group of six sat and ate beneath a stūpa, and after finishing, they left food and grass defiling the ground and departed. The fault was reported to the Buddha, who thereupon formulated [the rule] that one must not sit and eat [there]. Later, when constructing a stūpa or building rooms, or when ponds, wells, or food were donated, the seating of the assembled Saṃgha became crowded; [the Buddha] permitted sitting and eating beneath the stūpa, provided that one must not defile the ground.