Suppose there was a sea-faring ship bound together with ropes. For six months they deteriorated in the water. Then in the cold season it was hauled up on dry land, where the ropes were weathered by wind and sun. When the monsoon clouds soaked it with rain, the ropes would readily collapse and rot away. In the same way, when a mendicant is committed to development their fetters readily collapse and rot away.”

Numbered Discourses 7.72 7. The Great Chapter The Simile of the Great Mass of Fire

So I have heard. At one time the Buddha was wandering in the land of the Kosalans together with a large Saṅgha of mendicants.

While walking along the road, at a certain spot he saw a great mass of fire burning, blazing, and glowing. Seeing this he left the road, sat at the root of a tree on a seat spread out, and addressed the mendicants: “Mendicants, do you see that great mass of fire burning, blazing, and glowing?”

“Yes, sir.”

“What do you think, mendicants? Which is better—to sit or lie down embracing that great mass of fire? Or to sit or lie down embracing a girl of the aristocrats or brahmins or householders with soft and tender hands and feet?”

“Sir, it would be much better to sit or lie down embracing a girl of the aristocrats or brahmins or householders with soft and tender hands and feet. For it would be painful to sit or lie down embracing that great mass of fire.”