not sure but think this may be the source, if I, or another dreamt it?
PTS: A iii 138
"'Come, friends, be virtuous. Dwell restrained in accordance with the Patimokkha, consummate in your behavior & sphere of activity. Train yourselves, having undertaken the training rules, seeing danger in the slightest faults.' Thus they should be encouraged, exhorted, & established in restraint in accordance with the Patimokkha.
"'Come, friends, dwell with your sense faculties guarded, with mindfulness as your protector, with mindfulness as your chief, with your intellect self-protected, endowed with an awareness protected by mindfulness.' Thus they should be encouraged, exhorted, & established in restraint of the senses.
He who knows only his own side of the case knows little of that. His reasons may be good, and no one may have been able to refute them.
But if he is equally unable to refute the reasons on the opposite side, if he does not so much as know what they are, he has no ground for preferring either opinion …
He must be able to hear them from persons who actually believe them … he must know them in their most plausible and persuasive form.