Reference: Our current chapter 21 was originally part of the same chapter as our current chapter 20. One of the literary techniques displayed in that chapter was the explanation of information that is capped by a reference to a previously noted verse in Isaiah. This verse is a continuation of that technique. The verse referenced is:
Isaiah 52:15
15 So shall he sprinkle many nations; the kings shall shut their mouths at him: for that which had not been told them shall they see; and that which they had not heard shall they consider.
This verse was referenced as recently as 3 Nephi 20:45.