[21] Now at that time a certain bhikkhu, having enticed a female monkey with food in the Mahāvana at Vesālī, engaged in sexual intercourse (methuna dhamma) with her. Then that bhikkhu, when it was morning, having dressed and taking his bowl and robe, entered Vesālī for alms. Now at that time several bhikkhus, wandering on a tour of the lodgings, approached that bhikkhu's dwelling. The female monkey saw those bhikkhus coming while they were still far off; having seen them, she approached those bhikkhus, and in front of those bhikkhus she wiggled her hips, wiggled her tail, presented her hips, and made a suggestive sign. Then it occurred to those bhikkhus: "Without doubt this bhikkhu engages in sexual intercourse with this female monkey," and they concealed themselves to one side. Then that bhikkhu, having walked for alms in Vesālī, returned taking his almsfood. Then the female monkey approached that bhikkhu. Then that bhikkhu, having eaten one portion of that almsfood, gave one portion to the female monkey. Then the female monkey, having eaten that almsfood, presented her hips to that bhikkhu. Then that bhikkhu engaged in sexual intercourse with her.
Then those bhikkhus said to that bhikkhu: "Friend, has not a training rule (sikkhāpada) been laid down by the Blessed One? Why, friend, do you engage in sexual intercourse with this female monkey?"
"It is true, friend, that a training rule has been laid down by the Blessed One; but that concerns a human woman, not a female animal."
"Friend, is it not just the same? It is unfitting, friend, unbecoming, unsuitable, unworthy of an ascetic, improper, not to be done. How could you, friend, having gone forth in a Dhamma and Discipline so well proclaimed, be unable to live the holy life (brahmacariya), complete and pure, for as long as life lasts? Has not the Dhamma been taught by the Blessed One in many ways for dispassion, not for passion … the allaying of the fevers of sensual desires been declared? This, friend, is neither for the confidence of those without confidence nor for the increase of those with confidence; rather, friend, it is for the lack of confidence of those without confidence and for the vacillation of some who have confidence."
Then those bhikkhus, having rebuked that bhikkhu in many ways, reported this matter to the Blessed One.
English translation from the Pali (Siam Raṭṭha edition) — under review, not for citation.