Day 17 covers all of Chapter 12, Devadatta, and opens Chapter 13, Encouragement for Keeping this Sutra.

Having last month learned who the seer who taught the king was, we hear the prediction for Devadatta’s future and the future of those who receive this chapter.

He said to the four kinds of devotees:

“Devadatta will become a Buddha after innumerable kalpas.’ He will be called Heavenly-King, the Tathāgata, the Deserver of Offerings, the Perfectly Enlightened One, the Man of Wisdom and Practice, the Well-Gone, the Knower of the World, the Unsurpassed Man, the Controller of Men, the Teacher of Gods and Men, the Buddha, the World-Honored One. The world of that Buddha will be called Heavenly-Way. That Buddha will live for twenty intermediate ka]pas. He will expound the Wonderful Dharma to all living beings. [Hearing the Dharma from him,] as many living beings as there are sands in the River Ganges will obtain Arhatship; another group of innumerable living beings will aspire for the enlightenment of cause-knowers; and another group of living beings as many as there are sands in the River Ganges will aspire for unsurpassed enlightenment, obtain the truth of birthlessness, and reach the stage of irrevocability. After the Parinirvana of Heavenly-King Buddha, his right teachings will be preserved in that world for twenty intermediate kalpas. During that time a stupa of the seven treasures sixty yojanas tall and forty yojanas wide and deep will be erected to enshrine the śarīras of his perfect body. Gods and men will bow to the wonderful stupa of the seven treasures and offer various flowers, incense powder, incense to burn, incense applicable to the skin, garments, necklaces, banners, streamers, jeweled canopies, music and songs of praise [to the stupa]. [By doing all this,] innumerable living beings will attain Arhatship; another group of innumerable living beings will attain Pratyekabuddhahood; and another group of inconceivably numerous living beings will aspire for Bodhi and reach the stage of irrevocability.”

He said to the bhikṣus:

“Good men or women in the future who hear this chapter of Devadatta of the Sūtra of the Lotus Flower of the Wonderful Dharma with faithful respect caused by their pure minds, and have no doubts [about this chapter], will not fall into hell or the region of hungry spirits or the region of animals. They will be reborn before the Buddhas of the worlds of the ten quarters. They will always hear this sūtra at the places of their rebirth. Even when they are reborn among men or gods, they will be given wonderful pleasures. When they are reborn before the Buddhas, they will appear in lotus-flowers.”

Nichiren offers this explanation of why Devadatta’s sins did not preclude his becoming a Buddha in the Lotus Sūtra:

[R]egarding the three rebellious sins committed by Devadatta, although he caused the Buddha to bleed, this Buddha was the Buddha before the Lotus Sūtra was preached and not the Original and True Buddha who attained Enlightenment in the eternal past. He also killed an arhat, but this arhat was the one before the Lotus Sūtra was preached, not the practicer of this sūtra. He disrupted the harmony in a Buddhist order, but it was not the order based on the great sudden and perfect Lotus precepts, but on the Hinayana precepts before the Lotus Sūtra was preached. As a result, although the earth split open and Devadatta fell into the Hell of Incessant Suffering, because he had not actually committed the three rebellious sins against the Lotus Sūtra, he could therefore still become the Heavenly King Buddha in the Lotus Sūtra.

Ha Ryōkan-tō Gosho, A Letter Refuting Ryōkan-bō and Others, Writings of Nichiren Shōnin, Volume 5, Pages 55-56

Day 16 concludes Chapter 11, Beholding the Stūpa of Treasures, and completes the Fourth Volume of the Sūtra of the Lotus Flower of the Wonderful Dharma.

Having last month heard Śākyamuni ask in gāthās who will protect this teaching, we consider how difficult it is to expound this sūtra.

Good men! Think this over clearly!
It is difficult
[To expound this sūtra].
Make a great vow to do this!

It is not difficult
To expound all the other sūtras
As many as there are sands
In the River Ganges.

It is not difficult
To grasp Mt. Sumeru
And hurl it to a distance
Of countless Buddha-worlds.

It is not difficult to move [a world]
[Composed of] one thousand million Sumeru-worlds
With the tip of a toe
And hurl it to another world.

It is not difficult
To stand in the Highest Heaven
And expound innumerable other sūtras
To all living beings.

It is difficult
To expound this sūtra
In the evil world
After my extinction.

It is not difficult
To grasp the sky,
And wander about with it
From place to place.

It is difficult
To copy and keep this sūtra
Or cause others to copy it
After my extinction.

It is not difficult
To put the great earth
On the nail of a toe
And go up to the Heaven of Brahman.

It is difficult
To read this sūtra
Even for a while in the evil world
After my extinction.

It is not difficult
To shoulder a load of hay
And stay unburned in the fire
At the end of the kalpa [of destruction].

It is difficult
To keep this sūtra
And expound it to even one person
After my extinction.

It is not difficult
To keep the store
Of eighty-four thousand teachings
Expounded in the sūtras
Composed of the twelve elements,
And expound it to people,
And cause the hearers to obtain
The six supernatural powers.

It is difficult
To hear and receive this sūtra,
And ask the meanings of it
After my extinction.

It is not difficult
To expound the Dharma
To many thousands of billions of living beings
As many as there are sands
In the River Ganges
So that they may be able
To obtain the benefits:
Arhatship and the six supernatural powers.

It is difficult
To keep
This sūtra
After my extinction.

Since I attained
The enlightenment of the Buddha,
I have expounded many sūtras
In innumerable worlds.

This sūtra is
The most excellent.
To keep this sūtra
Is to keep me.

Nichiren offers this on the value of the Stupa of Treasures and the testimony of Many Treasures Buddha and the innumerable Buddhas all over the universe.

Although the Lotus Sūtra consists of only eight fascicles, it is as valuable as reading 16 fascicles because it is the teachings expounded by both Śākyamuni Buddha and the Buddha of Many Treasures. These 16 fascicles in turn hold the value of innumerable fascicles because they were verified by innumerable Buddhas all over the universe. In other words, a single character of the Lotus Sūtra is as valuable as two characters because it was confirmed by the two Buddhas, Śākyamuni and Many Treasures. It is equal to the value of numerous characters because it was verified by numerous Buddhas all over the universe. Just as treasures produced by a wish-fulfilling gem hold the equivalent value as those produced by numerous gems, the merit of one character of the Lotus Sūtra is as valuable as those of numerous characters.

Nichimyō Shōnin Gosho, A Letter to Nichimyō Shōnin, Writings of Nichiren Shōnin, Volume 4, Faith and Practice, Page 138