“‘Brethren, if outsiders should speak against me, or against the Doctrine, or against the Order, you should not on that account either bear malice, or suffer heart-burning, or feel ill will. If you, on that account, should be angry and hurt, that would stand in the way of your, own self-conquest. If, when others speak against us, you feel angry at that, and displeased, would you then be able to judge how far that speech of theirs is well said or ill?’
‘That would not be so, Sir.’
‘But when outsiders speak in dispraise of me, or of the Doctrine, or of the Order, you should unravel what is false and point it out as wrong, saying: “For this or that reason this is not the fact, that is not so, such a thing is not found among us, is not in us.”
‘But also, brethren, if outsiders should speak in praise of me, in praise of the Doctrine, in praise of the Order, you should not, on that account, be filled with pleasure or gladness, or be lifted up in heart. Were you to be so that also would stand in the way of your self-conquest. When outsiders speak in praise of me, or of the Doctrine, or of the Order, you should acknowledge what is right to be the fact, saying: “For this or that reason this is the fact, that is so, such a thing is found among us, is in us.””

T. W. Rhys Davids trans. (1899), Brahmajāla Sutta, verse 1.5-6 https://en.wikisource.org/wiki/Brahmajala_Sutta#Brahmaj.C4.81la_Sutta_.5B9.5D_-_The_Perfect_Net (text at archive.org https://archive.org/stream/bookofdiscipline02hornuoft#page/3/mode/1up), as cited in: (1992). A Comparative History of Ideas, p. 221-2 <br class="br">Source: Pali Canon, Sutta Pitaka, Digha Nikaya (Long Discourses)