On Yuan Chwang's Travels in India, 629–645 A.D. v1.c8.s6.8

v1.c8.s6.8

It is evident that Yuan-chuang, like other non-Indian Buddhists, had been taught to regard the spoken and written language of "Mid-India" as at once the parent and the standard of all the dialects of "North-India". These latter had departed a little from the correct form in their writing, some of them, as in Gandhāra, having written alphabets so unlike the parent one that they had special names. In oral speech the border lands and outlying regions generally had come to differ much from the people of "Mid-India". They had lost the rich purity of the standard language, and had persisted in erroneous forms of expression until these had come to be taught as the rule.