Although the world in which he appears will not be an evil one, that Buddha will expound the teaching of the Three Vehicles according to his original vow.

The teaching of the three vehicles was designed originally for the impure ages. Now that the lands have been purified, there is no need for the three. But why does [the Buddha] speak of the three? He wants to show that the three are identical with the One; there is no separate “three” anymore. What he formerly understood as three is the One; hence, former vow. He did not really mean to preach the three kinds of transformative teaching as such.