Mbh 13.26.4

"'Bhishma said, "In this connection is cited the old narrative of a conversation between a Brahmana in the observance of the Sila and the Unccha vows, O Yudhishthira, and a Rishi crowned with ascetic success. Once on a time, a foremost person, having roamed over this entire earth adorned with mountains, arrived at last in the house of a foremost person leading the domestic mode of life in accordance with the Sila vow. The latter welcomed his guest with due rites. Received with such hospitality, the happy Rishi passed the night happily in the house of his host. The next morning the Brahmana in the observance of the Sila vow, having finished all his morning acts and rites and purified himself duly, very cheerfully approached his guest crowned with ascetic success. Meeting with each other and seated at their ease, the two began to converse on agreeable subjects connected with the Vedas and the Upanishads. Towards the conclusion of the discourse, the Brahmana in the observance of the Sila vow respectfully addressed the Rishi crowned with success. Endued with intelligence, he put this very question which thou, O Yudhisthira, hast put to me.