संस्कृते विश्वासटिप्पन्यः

In many places where BHS differs from Sanskrit it is closer to, or identical with, Pāli.
However, earlier works, mostly from the Mahāsāṃghika school, use a form of “mixed Sanskrit” in which the original Prakrit has been incompletely Sanskritised, with the phonetic forms being changed to the Sanskrit versions, but the grammar of Prakrit being retained. For instance, Prakrit bhikkhussa, the possessive singular of bhikkhu (monk, cognate with Sanskrit bhikṣu) is converted not to bhikṣoḥ as in Sanskrit but mechanically changed to bhikṣusya.