[340] Then that bhikkhu, not satisfied with that bhikkhu's answering of the question, approached the Blessed One; having approached and paid homage to the Blessed One, he sat down to one side. Sitting to one side, that bhikkhu said this to the Blessed One: "Here, venerable sir, I approached a certain bhikkhu; having approached, I said this to that bhikkhu: 'In what way, friend, is a bhikkhu's vision (dassana) well purified?' When this was said, venerable sir, that bhikkhu said this to me: 'When, friend, a bhikkhu understands as it really is the origin and the passing away of the six bases of contact (phassāyatana), in that way, friend, a bhikkhu's vision is well purified.' Then, venerable sir, not satisfied with that bhikkhu's answering of the question, I approached a certain bhikkhu; having approached, I said this to that bhikkhu: 'In what way, friend, is a bhikkhu's vision well purified?' When this was said, venerable sir, that bhikkhu said this to me: 'When, friend, a bhikkhu … of the five aggregates subject to clinging … understands as it really is the origin and the passing away of the four great elements (mahābhūta) … understands as it really is: "Whatever is subject to origination, all that is subject to cessation" — in that way, friend, a bhikkhu's vision is well purified.' Then, venerable sir, not satisfied with that bhikkhu's answering of the question, I approached the Blessed One … In what way, venerable sir, is a bhikkhu's vision well purified?"
English translation from the Pali (Siam Raṭṭha edition) — under review, not for citation.