1 Nephi 5:19

Wherefore he said that these plates of brass should never perish; neither should they be dimmed any more by time. And he prophesied many things concerning his seed.

So he said these brass plates would never be destroyed. Time would never damage them. He prophesied many things about his children.

He said these brass plates would never be destroyed. Time would never fade them. He prophesied many things about his descendants.