2 Nephi 25:7

But behold, I proceed with mine own prophecy, according to my plainness; in the which, I know that no man can err; nevertheless, in the days that the prophecies of Isaiah shall be fulfilled, men shall know of a surety, at the times when they shall come to pass;

I will tell you my own prophecy. I will speak plainly. No one can make a mistake about what I say. But one day Isaiah’s prophecies will come true. When that happens, people will know for sure that they are real.

I’m moving ahead with my own prophecy now, speaking as plainly as I can. I know no one can miss what I’m saying. When Isaiah’s prophecies come true, people will know for certain—because the events themselves will make it obvious.