More from Reverend Tsuchiya's commentary on Chapter 16 of the Lotus Sutra, The Lifespan of the Tathagata.

Lotus Sutra Chapter 16

"To save people,

I enter to Nirvana as an expedient.

However, I will not pass into Nirvana actually.

I am always here and preaching the truth.

Although I am always here,

by my supernatural powers,

people who are upset cannot see me even if I am near."

(Significance)-1

It shows that the Buddha Sakyamuni is active timelessly of 'no beginning, no end', mainly in the present, also from the past to the future. Although the immortal Tathagata always is in this Saha world to save people, he shows entering Nirvana as an expedient to educate people. The reason is that he cannot save people if he is always here. It is impossible to save people if they do not cause the mind of adoring the Buddha. Even if the Buddha is always here, you will not be saved with just that. You will be saved by adoring the Buddha and by practicing virtue and good deeds. If you behave like a spoiled child and become lazy more and more because Tathagata is always at your side, it is impossible to achieve the purpose of saving people. Therefore, Tathagata disappears temporarily to let people cause the mind of adoring, entering to Nirvana for educating people. However, "I will not pass into Nirvana actually", the main body of Tathagata never goes out of existence. He is the permanent Tathagata who is always here and preaching the truth. Even if there are persons who do not see him, he continues to educate people who hope it. "Although I am always here", he is always in the Saha world but "By my supernatural powers, people who are upset cannot see me even if I am near." With mysterious powers, Tathagata does not appear in the naked eye of upset people although he is at their side, because it is necessary to let people keep the mind of adoring. If you recover yourself by closing your eyes, and adore him, you can recognize the real existence of Tathagata. Even if you see him with the eyes, it comes to nothing as long as you do not adore him. People becoming upset tend to forget to improve the eternal spirit by being tempted to worldly desires. If you think that you are saved by Tathagata anytime, you will repeat the mistakes saying, "I will do it someday." Therefore, he stimulates the mind of adoring by hiding himself. It is very important that the Buddha Sakyamuni says, "I am always here", that is not heaven or the Western Paradise. Although Tathagata can stay anywhere, he is at your side. Although he is the eternal Buddha being active in the world of ten directions, he is not far away from you and protecting  you at your side. Those warm words of kindness are very appreciated by us.