Śākyamuni Buddha preached an important principle about the three venerables: lord, master and parents, in the third chapter on the “Parable” of the Lotus Sūtra.

This is the essence of the sūtra. In this sūtra it is said: “Now this Sahā World is all My domain, where all the people are My children. However, this world is full of various sufferings, and it is I, Śākyamuni Buddha, alone who can save them.” To those against the Lotus Sūtra, it preaches: “Those who do not listen to the Buddha when He taught and tried to persuade them that they are slanderers of the dharmas will all fall into the Hell of Incessant Suffering without fail.”

Shimoyama Goshōsoku, The Shimoyama Letter, Writings of Nichiren Shōnin, Volume 5, Page 91-92