Day 21 covers all of Chapter 16, The Duration of the Life of the Tathāgata.
All of you, wise men!
Have no doubts about this!
Remove your doubts, have no more!
My words are true, not false.The physician, who sent a man expediently
To tell his perverted sons
Of the death of their father in order to cure them,
Was not accused of falsehood although he was still alive.In the same manner, I am the father of the world.
I am saving all living beings from suffering.
Because they are perverted,
I say that I pass away even though I shall not.
If they always see me,
They will become arrogant and licentious,
And cling to the five desires
So much that they will fall into the evil regions.I know who is practicing the Way and who is not.
Therefore I expound various teachings
To all living beings
According to their capacities.I am always thinking:
“How shall I cause all living beings
To enter into the unsurpassed Way
And quickly become Buddhas?”