"Selections from DOCTRINES OF SALVATION" by Joseph Fielding Smith, pages 437,438
The Millennium
Resurrection of righteous at beginning of Millennium.
Again, when the Lord comes, not only is this change going to come to the earth and to those who remain upon the earth, to the fish of the sea, to the fowl of the air, and the beasts upon the earth, but the graves are to be opened, and the righteous dead, they who have kept the commandments of the Lord, are going to come forth; they shall receive their resurrection no matter when they have lived (see D&C 76:50-80; 88:96-99; Revelation 20:4-6)
All those who have died in Christ shall come forth from the dead at his coming and shall dwell upon the earth as Christ shall be upon the earth during this millennium. They shall not remain here all the time during the thousand years, but they will mingle with those who are still here in mortal life (see Joseph Smith, Teachings of the Pro phet Joseph Smith, sel. Joseph Fielding Smith [1976], 268-69). These resurrected saints and the Savior himself, shall come to give instruction and guidance; to reveal unto us the things we ought to know; to give us information concerning the work in the temples of the Lord so we may do the work which is essential to the salvation of worthy men.
It matters not so far as we are concerned whether we die before that day comes or are living on the earth, for if we die in righteousness we shall be raised in the resurrection of the just, and shall be caught up to meet Christ in the clouds of glory when he comes to take possession of the earth, as King of kings and Lord of lords. This is the gospel of Jesus Christ. It is declared in the revelations of the Lord which are found in the Bible and the Doctrine and Covenants. [DS 3:59.]
Wicked remain in spirit prison during Millennium.
However, if we have not kept the commandments of the Lord, if we have been unjust, and lovers of sin and our hearts have been set upon evil; then we shall die and shall not live again until the thousand years are ended (see D&C 76:81-88, 98-112; 88:100-102). It is decreed that the unrighteous shall have to spend their time during this thousand years in the prison house prepared for them where they can repent and cleanse themselves through the things which they shall suffer.
John, in his great vision, saw the rest of the dead and they lived not again until the thousand years were ended (see Revelation 20:5). That is a calamity---it is a dreadful thing to contemplate, for there shall be a great host of men swept off the face of the earth because of their wickedness. The bodies of these will have to remain in the grave and their spirits in the spirit house to be taught repentance and faith in God while the thousand years of peace are progressing upon the earth.
I wish, my good brethren and sisters, that we would read these revelations, that we would make ourselves more familiar with that which they contain, for there shall be a judgment when Christ comes (see Matthew 25:31-46). We are informed that the books shall be opened, the dead shall be judged out of the things which are written in the books and among the books will be the book of life. We shall see its pages; we shall see ourselves just as we are. And we are to understand with a righteous understanding that the judgments which are meted out to us are just and true, whether we come into the kingdom of God, to receive these glorious blessings, or whether we are banished into the realm of the dead (see Revelation 20:11-15; 2 Nephi 9:10-16, 46). [DS 3:59-60.]