Sakyamuni begins [Chapter 16, The Duration of the Life of the Tathāgata,] by appealing three times for his listeners to “understand my sincere and infallible words by faith.” To this appeal, all the Bodhisattvas headed by Maitreya responded each time, “World-Honored One, tell us! We will receive your words by faith.” Then Sakyamuni replied, “Listen to me attentively! I will reveal to you my hidden core and supernatural powers” (p. 241).

Here “hidden core” means his deepest innermost self, and “supernatural powers” are actions outflowing from that hidden core.