This story is from Master Hsuan Hua‘s commentary on the Medicine Master Sūtra.

All things are impermanent,
Coming into being and ceasing to be.
When coming into being and ceasing to be both stop,
There is blissful quiescence.

In the past, Śākyamuni Buddha offered up his life for half of this four-line verse. How did it happen? When he was cultivating in a past life, he met a being from the Heaven of Pure Dwelling who manifested as a rākṣasa ghost to test the his sincerity. The rākṣasa ghost walked by the old cultivator chanting to himself, “All things are impermanent, coming into being and ceasing to be.”

The cultivator thought, “What’s he singing? Oh, it’s a verse” Then he asked the ghost, “Hey, what did you just say?”

“I said, ‘All things are impermanent, coming into being and ceasing to be.”” Replied the ghost.

“Aren’t there two more lines to your verse?”

“Yes,” said the ghost.

“Please tell me what they are.”

“I’m starving, I don’t have any energy,” said the ghost. “If you give me something to eat, I’ll tell you.”

“Okay,” said the cultivator. “I’ll offer you whatever you want, and then you can tell me those two lines.”

The rākṣasa ghost said, “I need to eat the flesh and drink the blood of a living human being. Can you give up your own flesh and blood?”

The cultivator thought, “Well, if I get to hear the Dharma, then my death will be worth it. But if I don’t get to hear those two lines of verse, I’ll never be able to put everything down.” And so the cultivator replied, “Fine, tell me the rest of the verse, and then I’ll let you eat me.”

“Okay,” said the ghost. “The last two lines are: ‘When coming into being and ceasing to be both stop, there is blissful quiescence.’ Everything in the world is impermanent, coming into being and ceasing to be. The attainment of what neither comes into being nor ceases to be is true and eternal happiness. Okay, now I’m going to eat you.”

“Hold on!” said the cultivator. “Don’t eat me yet.”

“What? Are you going back on your promise?”

“No, no. I’m not going back on my promise. I just want to carve this verse on a tree, so it will remain in the world. When people see it, they will bring forth the Bodhi mind and eventually attain the Path.”

“That sounds like a good idea,” the rākṣasa ghost said. “Go ahead and carve it.”

The cultivator scraped off the outer bark of a tree with a knife and carved the verse onto the tree. Meanwhile, the rākṣasa began wailing, “Please hurry! I’m famished!”

After the cultivator quickly finished carving, the rākṣasa said, “I’m not going to be polite anymore. I must eat your flesh and drink your blood.”

“Hold on,” said the cultivator. “Please wait a bit longer.”

“What? You’ve taken so long already. What else do you want to do?” complained the ghost.

The cultivator said, “The words on the tree will eventually be worn away by the elements. I want to chisel this verse in stone so that it will last forever. Please be patient for a little while longer as I do this.”

“Oh, all right,” said the rākṣasa.

When the cultivator finished chiseling, the rākṣasa said, “Now I can eat you!”

“Fine,” said the cultivator, as he closed his eyes and waited to be eaten.

Suddenly a voice in space said, “Bravo! You are a true cultivator who is able to sacrifice himself for the Dharma. You will certainly become a Buddha.” When the cultivator opened his eyes, the rākṣasa ghost was gone and a god from the Heaven of Pure Dwelling appeared before him.

That is known as “not being afraid to renounce one’s life for half a verse.” Could we be that sincere in our study of Buddhism? Could we renounce our lives for half a verse or for a sūtra?