四分律行事鈔資持記 3.420

3.420

《五分》，初明淨不淨地，即人物俱在二界之間。非所為者，謂非作意觸等。若下，次明物在不淨地，約知不知。初引緣。不下，佛斷。

In the Mahīśāsaka-vinaya, the first [part] explains pure and impure ground, which is when the person and the item are both between two boundaries. "Not done deliberately" refers to touching and so forth not done with intention. From "If..." onward, it next explains items in an impure ground, evaluated according to knowing or not knowing. First it cites the circumstantial origin. From "Not..." onward, the Buddha makes the determination.