In Vinaya, Cullavagga, the Buddha advises bhikkhus not to use Vedic language (Chanda; i.e. Vedic Sanskrit) (Vin. II, PTS, p. 139 “Chandaso”) for the Buddha’s language/teachings (buddhavacana), but use your own language (sakāya niruttiyā) for the Buddha’s teachings. If making the Vedic language for the Buddha’s teachings, it will be corrupt.
The essential teaching here is “sakāya niruttiyā” (based on your own language) for the Buddha’s teachings “Buddhavacana”. No any languages, including Pali, should be regarded as an absolute Buddhavacana.
This understanding is very essential for the studies in EBTs or Early Buddhism.