四分律刪繁補闕行事鈔 1.146

1.146

別住者，昔云同一界不盡集，今謂界外比丘濫將入數。非謂眼見在界外，以界分不知，冥然在外，作法不成，故云不足。

Undergoing parivāsa: formerly it was said to mean not completely assembling within the same boundary; now it refers to mistakenly including bhikṣus outside the boundary in the count. It does not mean seeing them with one's eyes outside the boundary; because the boundary limits are not known, and they are unseen outside, the performance of the act is invalidated, and thus it is said that they do not make up the quorum.