四分律刪繁補闕行事鈔 2.137

2.137

十五井界。《僧祇》：道行露地井蘭旁宿，置衣在二十五肘內，身在外者，失衣。衣在井中，應繩連，垂手繩井中，得會衣；與井上界別也。以此例餘坑窨窖等。

Fifteenth is the well boundary (kūpa-sīmā). The Mahāsāṃghika states: When traveling on a road, sleeping beside an open well-parapet, if one places the robes within twenty-five cubits and one's body is outside, one forfeits the robes. If the robes are in the well, one should connect them with a rope and hang one's hand on the rope into the well, whereby one manages to meet the robes; it is distinct from the boundary above the well. By this analogy, other pits, underground cellars, and vaults are likewise.