四分律行事鈔資持記 2.1069

2.1069

次科，彼宗開病，限至三家，但開背二；若容更背，恃開無節，教緩機慢，故不得四也。

In the next section, that school permits an exception for illness, limited to three families, but only permits turning one's back on two; if it allowed turning one's back further, relying on the exception without moderation, the teaching would become lax and the practitioner careless, so one cannot reach four.