It’s one of Bossuet’s most famous quotations, and in my opinion his best. It comes from his discussion of the nature of the Magi, some of which is here:
The Magi, are they absolute kings or dependent on a greater empire? or are they only great lords, which gave them the name of kings, according to the custom of their country? Or are they only sages, philosophers, the arbiters of religion in the empire of the Persians or, as it was called then, in that of the Parthians, or in some part of this empire which extended by all the East? Do you think I am going to resolve these doubts and satisfy your curious desires? You are wrong; I did not take pen in hand to teach you the thoughts of men; I will only tell you that they were the scholars of their country, observers of the stars, whom God takes by their attraction, rich and powerful, as their presents make it appear; if they were among those who presided over religion, God had made himself known to them, and they had renounced the worship of their country.
Bossuet, Elevations on the Mysteries, XVI, 3
Positive Infinity 