Great are the words of Isaiah 3 Nephi 23: 1-5

1 AND now, behold, I say unto you, that ye ought to search these things. Yea, a commandment I give unto you that ye search these things diligently; for great are the words of Isaiah.
2 For surely he spake as touching all things concerning my people which are of the house of Israel; therefore it must needs be that he must speak also to the Gentiles.
3 And all things that he spake have been and shall be, even according to the words which he spake.
4 Therefore give heed to my words; write the things which I have told you; and according to the time and the will of the Father they shall go forth unto the Gentiles.
5 And whosoever will hearken unto my words and repenteth and is baptized, the same shall be saved. Search the prophets, for many there be that testify of these things.

(Book of Mormon | 3 Nephi 23:1 - 5)

Jesus stresses to the people the importance of the words of Isaiah. He commands that we search them diligently. Isaiah is quoted frequently in the New Testament as well as the Book of Mormon, and obviously it is written in the Old Testament.

This should not be taken lightly. Many, including myself at times, finds Isaiah’s words to be cryptic and difficult to follow. Accordingly, there can be a tendency to skip over it for the easier to understand scriptures.

The scriptures teach, Where much is given, much is required, see D&C 82:3. I would suggest that the opposite is also true, i.e. Where much is required much is given. It takes very thoughtful study and the Spirit to understand the words of Isaiah. But, if we pay the price to diligently study his words, as we’re commanded to do, we will obviously reap great benefits. There are study guides and books (like the picture above) available to glean gospel truths from his words.