This future day will bring a world full of prophets and prophetesses. We will no longer have any need for teachers. As Paul wrote in Hebrews 8: 11:
"And they shall not teach every man his neighbour, and every man his brother, saying, Know the Lord: for all shall know me, from the least to the greatest."
Everyone will be taught in that day by the Perfect Teacher, the descendant of Jesse, through David, who will stand as the great ensign to the world. When He comes He will teach us all things. The earth will rest, and men and women will be preparing under His personal tutelage for the final Day of Judgment, when Christ will deliver us up as His finished product to the Father.
His rest shall be "glorious" because He will have redeemed and presented us to the Father as candidates for eternal life. The great work of the Father, to bring to pass the immortality and eternal life of us all, will be accomplished for all the faithful through Christ. It will be "glorious" indeed. All those who are redeemed will celebrate, worship and praise Him.
“His Rest Shall Be Glorious”
The "root of Jesse" is a reference to the father of King David. David, King of Israel, founded the lineage of kings whose dynasty would last until the Jews lost their kingdom. When Christ was born, His mother Mary's, lineage, and His father Joseph's, lineage, made Him a "Son of David" and, therefore also a direct descendant of Jesse. Christ was directly involved in the Restoration of His Church. He appeared with the Father in the First Vision. He provided supervising authority over all the events of the Restoration. He appeared in the Kirtland Temple as the Restoration approached the initial completion, to supervise personally the final return of keys, which followed immediately after. He appeared again in the Salt Lake Temple to President Lorenzo Snow. In vision, Joseph F. Smith saw Christ's ministry to the Spirit World. And He has appeared elsewhere to others. This latter-day restoration work is a product of Christ's direct involvement and ultimate presiding direction under the Father.
Nephi foresaw He would create an "ensign" in the last days, and "to it shall the Gentiles seek." A great sign or invitation has been given from Him. Initially, those who have been gathering are "Gentiles" whose distant association with scattered Israel has been long ago forgotten. They come as "Gentiles," but become again a latter-day reconstruction of the family of Israel. Nephi saw and wrote about this. These words from Isaiah offer a second witness and testimony to confirm what Nephi saw. Nephi is vindicating his own message with this reinforcing language from Isaiah.