4 The preservation of the Christian faith among the Hindus will be precarious and its propagation uncertain as long as there is not a native clergy properly trained for priestly duties, not only to be of assistance to foreign priests, but also to be in rightful charge of the administration of the Christian Church in their cities. Tradition tells us that Frances Xavier maintained this same opinion. They say that he used to assert that the Christian cause in India could never have firm roots without the continuing dedication of a pious and zealous clergy native to India. It is clearly evident that he had a keen understanding of the issue. Certainly the work of the missionaries coming from Europe is beset with many obstacles. Most especially, indeed, is their unfamiliarity with the vernacular, which is very difficult to learn. There is also the remoteness of institutions and customs which remain unfamiliar even after a long period of time. Hence, the European clergy is forced to live there as in a strange land. Since a foreign clergy, therefore, has difficulty in winning the hearts of the people, it is plain that the work of a native clergy would be far more fruitful. From experience, they know the nature and customs of their people; they know when to speak and when to keep silent. In fine, they live among Hindus as Hindus without causing any suspicion and it is, indeed, difficult to say how important this is especially in times of crisis.
Source: Ad Extremas (Vatican.va)