[170] Then the Blessed One, having come out of the dwelling, began to walk up and down in meditation. Ambaṭṭha the young brahmin, too, having come out of the dwelling, walked up and down. Then Ambaṭṭha the young brahmin, while walking up and down following the Blessed One as he walked, scrutinized the Blessed One's body for the thirty-two marks of a great man. And Ambaṭṭha the young brahmin saw on the Blessed One's body the thirty-two marks of a great man for the most part, excepting two; concerning two of the marks of a great man he doubted, was uncertain, did not come to conviction, did not gain confidence: concerning the male organ enclosed in a sheath and the largeness of the tongue.
Then it occurred to the Blessed One: "This Ambaṭṭha the young brahmin sees on me the thirty-two marks of a great man for the most part, excepting two; concerning two of the marks of a great man Ambaṭṭha doubts, is uncertain, does not come to conviction, does not gain confidence: concerning the male organ enclosed in a sheath and the largeness of the tongue."
Then the Blessed One performed such a feat of psychic power (iddhābhisaṅkhāra) that Ambaṭṭha the young brahmin saw the Blessed One's male organ enclosed in its sheath. Then the Blessed One, extending his tongue, stroked back and forth over both ear openings, stroked back and forth over both nostril openings, and covered the whole circle of his forehead with his tongue.
English translation from the Pali (Siam Raṭṭha edition) — under review, not for citation.