The Buddha taught and transformed people with his compassion and wisdom, which could also be seen in the way he treated followers of other religions. The Buddha's and his followers' amicable relations with other religions can be illustrated by the following two excerpts.
As recorded in the Upali Sutta (No. 56, Middle Section), there was a wealthy householder called Upali, who was a lay follower of Nigantha Nataputta (the mentor of naked ascetics). Once, when he learnt that the Buddha's viewpoint on karma differed from that of his religion, he eagerly offered himself to go and refute the Buddha's doctrine. However, after a series of back and forth questions and answers, he was thoroughly convinced of the points expounded by the Buddha, and wholeheartedly made a vow to take refuge in the Three Jewels. The Buddha accepted him but stressed that he should continue to respect and support his old religious teachers, and said 'For a long time now, householder, your family has been like a fountain to the naked ascetics. Hence, you must bear in mind that alms should be given to those who come '*.
In the third century B.C., Emperor Asoka of India, a devout Buddhist who followed the teachings of the Buddha, honored and supported all religions equally in his empire. At the same time, he also fostered harmony and mutual learning among religions. The excerpt below from No. 12 of Emperor Asoka's Edicts Carved on Rocks provides strong evidence.
'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 benefts, 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 good2. One should listen to and respect the doctrines professed by others. '**
Today we wish to promote world peace and global unity. But where do we start? The Buddha and King Asoka have already demonstrated to us that world peace and global unity can be achieved if we start with unity and harmony among religions. In particular, Emperor Asoka's 12th Edict stated very clearly that followers of religions should not criticize each other; instead, they should study the religious teachings of one another.
Following the examples of the Buddha and King Asoka, members of the Hong Kong Buddhist Education Foundation selected 360 passages from various Buddhist sacred texts and compiled the passages in Buddhism 360, with the hope that we can help more people understand Buddhist education, as well as promote mutual learning among religions and contribute to social stability and harmony.
Chin Kung, AM, May 2016, Hong Kong
2. Ven. Walpola Sri Rahula translated 'ta samavayo eva sadhu ' as 'Concord is good. ' The Pali word 'samavaya ': [m.] combination; coming together.
* Upali Sutta. Sutta Central: https://suttacentral.net/en/mn56
**The Edicts of King Ashoka. An English rendering by Ven. S. Dhammika. The Wheel Publication No. 386/387 ISBN 955-24-0104-6 Published in 1993.