善知識 (Skt kalyana-mitra; Jpn zen-chishiki )
Also, good companion. One who leads others to the correct teaching, or helps them in their practice of the correct teaching. In this sense, good friend may also be called good teacher.
A good friend is contrasted with an evil friend, who leads people away from the way of Buddhist practice and into the evil paths, that is, into suffering. Buddhism teaches that, in pursuing the way to enlightenment, one should associate with a good friend to strengthen one's faith and practice.
In the "Devadatta" (twelfth) chapter of the Lotus Sutra, Shakyamuni Buddha describes Devadatta, who tried to kill him, as a good friend who in a past life instructed him in the Lotus Sutra.
Shakyamuni states that it is therefore because of Devadatta that he was able to attain enlightenment and save living beings.
The "King Wonderful Adornment" (twenty-seventh) chapter of the sutra describes the two brothers Pure Storehouse and Pure Eye as good friends to their father, King Wonderful Adornment, because they converted their father to the correct teaching.
This chapter defines a good friend as "the great cause and condition by which one is guided and led, and which enables one to see the Buddha and to conceive the desire for supreme perfect enlightenment."
See also evil friend.