佛制比丘六物圖 1.75

1.75

二、明勢分者。作法衣界則無，必須入界，方乃會衣。（勢分是自然，與作法界體異故。）十五種自然並隨界量外例加一十三步，計七丈八尺。（《善見》：「不健不羸人，　盡力擲石落處。」古德評之：約一十三步為準。）但入勢分，即成會衣，不必入界。（若有染、隔、情三礙在界，　即無勢分。）

Second, explaining the extended perimeter. Ritual robe-boundaries do not have one; one must enter the boundary itself before uniting with the robes. (This is because the extended perimeter is natural, and differs in nature from a ritual boundary.) For the fifteen kinds of natural boundaries, an additional thirteen paces—calculated as seven zhang, eight chi—is routinely added beyond their respective dimensions. (The Samantapāsādikā states: "The distance to which a person neither robust nor frail throws a stone with all his might." Ancient masters evaluated this: taking thirteen paces as the standard.) Merely entering the extended perimeter constitutes uniting with the robes; it is not necessary to enter the boundary proper. (If there are the three obstructions of defilement, physical barrier, or mental disquiet within the boundary, there is no extended perimeter.)