Atthavasasutta
“Tayo, bhikkhave, atthavase sampassamānena alameva paresaṁ dhammaṁ desetuṁ. Katame tayo? Yo dhammaṁ deseti so atthappaṭisaṁvedī ca hoti dhammappaṭisaṁvedī ca. Yo dhammaṁ suṇāti so atthappaṭisaṁvedī ca hoti dhammappaṭisaṁvedī ca. Yo ceva dhammaṁ deseti yo ca dhammaṁ suṇāti ubho atthappaṭisaṁvedino ca honti dhammappaṭisaṁvedino ca. Ime kho, bhikkhave, tayo atthavase sampassamānena alameva paresaṁ dhammaṁ desetun”ti.
Good Reasons
“Mendicants, taking three reasons into consideration provides quite enough motivation to teach Dhamma to another. What three? When the teacher understands the meaning and the teaching. When the audience understands the meaning and the teaching. When both the teacher and the audience understand the meaning and the teaching. Taking these three reasons into consideration provides quite enough motivation to teach Dhamma to another.”