3 Nephi 17:15

And when he had said these words, he himself also knelt upon the earth; and behold he prayed unto the Father; and the things which he prayed, cannot be written, and the multitude did bear record which heard him.

When he said these words, he kneeled on the ground too. He prayed to the Father. The things he prayed cannot be written. The crowd heard him and told others about it.

Then he knelt too and prayed to the Father. What he prayed cannot be written down. The crowd heard it and witnessed it.