Here’s what 3 Nephi 17 might’ve been like.
Jesus said He felt sad because of the sins of the house of Israel (see 3 Nephi 17:14).
In response, He did the same thing you might try when you’re feeling sad: He prayed!
The Nephites weren’t surprised to see the Savior praying, but they probably weren’t expecting what happened next.
PS—You can find all of the Book of Mormon videos here.