King Ashoka Rock edict #12:
Beloved-of-the-Gods, King Piyadasi, honors both ascetics and the householders of all religions, and he honors them with gifts and honors of various kinds. But Beloved-of-the-Gods, King Piyadasi, does not value gifts and honors as much as he values this -- that there should be growth in the essentials of all religions. Growth in essentials can be done in different ways, but all of them have as their root restraint in speech, that is, not praising one's own religion, or condemning the religion of others without good cause. And if there is cause for criticism, it should be done in a mild way. But it is better to honor other religions for this reason. By so doing, one's own religion benefits, and so do other religions, while doing otherwise harms one's own religion and the religions of others. Whoever praises his own religion, due to excessive devotion, and condemns others with the thought "Let me glorify my own religion," only harms his own religion. Therefore contact (between religions) is good. One should listen to and respect the doctrines professed by others. Beloved-of-the-Gods, King Piyadasi, desires that all should be well-learned in the good doctrines of other religions.
Those who are content with their own religion should be told this: Beloved-of-the-Gods, King Piyadasi, does not value gifts and honors as much as he values that there should be growth in the essentials of all religions. And to this end many are working -- Dhamma Mahamatras, Mahamatras in charge of the women's quarters, officers in charge of outlying areas, and other such officers. And the fruit of this is that one's own religion grows and the Dhamma is illuminated also.