By Sensuality
Kāmesu Sutta  (AN 5:7)

“For the most part, monks, beings are led astray by sensuality. When a son of good family, leaving behind the sickle & carrying pole, has gone forth from the household life into homelessness, he can be called one who has gone forth through conviction. Why is that? Because sensual pleasures, whether of this or that type, are obtainable by a youth. Inferior sensual pleasures, middling sensual pleasures, and superior sensual pleasures are all simply reckoned as ‘sensual pleasures.’

“It’s just as if a stupid baby boy, lying on its back, might—through the heedlessness of his nurse—take a stick or a piece of gravel into its mouth. The nurse would attend to him right away. Attending to him right away, she would take it out right away. If she couldn’t take it out right away, then holding his head in her left hand and crooking a finger of her right, she would take it out, even if it meant drawing blood. Why is that? There would be some injury to the boy—I don’t say that there wouldn’t—but the nurse should act in that way out of sympathy, wanting his well-being and seeking his benefit. But when the boy has grown and has enough discernment, the nurse can be unconcerned about him, [thinking,] ‘The boy can now look after himself. He won’t be heedless.’

“In the same way, as long as a monk is not developed in conviction with regard to skillful qualities, not developed in shame with regard to skillful qualities, not developed in compunction with regard to skillful qualities, not developed in persistence with regard to skillful qualities, and not developed in discernment with regard to skillful qualities, I have to look after him. But when he is developed in conviction with regard to skillful qualities, developed in shame with regard to skillful qualities, developed in compunction with regard to skillful qualities, developed in persistence with regard to skillful qualities, and developed in discernment with regard to skillful qualities, then I can be unconcerned about him, [thinking,] ‘The monk can now look after himself. He won’t be heedless.’”

See also: MN 58; MN 67; MN 122; Ud 3:3