Those are excellent questions and I trust the scriptures will give us the answer to them. First of all, there will be TWO CLASSES of believers in that day. We see that in Ephesians 1:10, “That in the dispensation of the fullness of the times He might gather together in one all things in Christ, BOTH which are IN HEAVEN and which are ON EARTH—in Him.” The “dispensation of the fullness of times” is the last dispensation when Christ will rule over the earth for 1,000 years (see Revelation 20:1-6). Christ will subdue all of His enemies (see Revelation 19:11-21) and then He will be worshipped as the “King of kings, and Lord of lords” by all of His redeemed “in heaven and on earth.” They will gladly “bow the knee before Him” as we see in Philippians 2:10-11, “That at the name of Jesus every knee should bow, of THOSE IN HEAVEN, and of THOSE ON EARTH, and of those under the earth, and that every tongue should confess that Jesus Christ is Lord, to the glory of God the Father.”  We see from this passage that all saints will be WORSHIPPING the Lord, but we will now quote scriptures to see what else they will be doing, or NOT doing. We will look at BOTH CLASSES separately because some of the answers will be different. Let’s consider “those in heaven” first.

1) They will be REIGNING with Christ: “And made them to our God kings and priests; and they shall REIGN OVER THE EARTH” (Revelation 5:10, DARBY Version). Believers will be living in the heavenly city, New Jerusalem (see Hebrews 10:22-23 & Revelation 21:9-10). They will “judge the world and angels” (1st Corinthians 6:2-3…NKJV).

2) They will NOT MARRY: “For in the resurrection they NEITHER MARRY nor are given in marriage, but are like the angels of God in heaven” (Matthew 22:30). Relationships in heaven will change dramatically, for there will be no marriages or the bearing of children. Our bodies will be made for heaven (see 1st Corinthians 15:35-49) yet the heavenly saints will be in the most intimate relationship of all, for they are the BRIDE OF CHRIST (see John 3:29; Ephesians 5:25-32; 2nd Corinthians 11:2 and Revelation 19:7-9).

3) They “may possibly” EAT: “Blessed are those who are called to the MARRIAGE SUPPER of the Lamb” (Revelation 19:9). Christ and His Bride will be married in heaven (though this will be unlike anything we’ve ever witnessed on earth) and Old Testament believers and those martyred during the Tribulation will be invited guests to the “marriage FEAST.” This “may” be a literal “feast of food” that will be eaten; if so, heavenly saints will eat. Yet it should be said that there won’t be the need to sustain one’s life by eating food since their heavenly bodies are immortal (see 1st Corinthians 15:50-53).

4) They will WORK: “And there shall be no more curse, but the throne of God and of the Lamb shall be in it, and His SERVANTS shall SERVE Him” (Revelation 22:3). There will be SERVICE in the heavenly city throughout the endless ages of eternity. As we saw earlier, believers in heaven will “reign with Christ” and “judge the world and angels” so there will be some form of work involved there. And there may be many other forms of service involving work. Yet we see in this verse that “there shall be no more curse” so any work that is done will be a pleasure without anything bad to hinder our enjoyment of serving our blessed Lord.

Regarding “those on earth,” I would ask you to read Isaiah 65:18-23 where we are given a picture of the saints on earth during the Millennium. We will get the answer to your questions in that passage, though there are many more that we could quote.

1) They will MARRY and have CHILDREN: “No more shall an INFANT from there live but a few days…for a CHILD shall die one hundred years old” (verse 20). Death will be rare during Christ’s 1,000-year reign and those who are born will live long. “They shall not labor in vain, nor BRING FORTH CHILDREN for trouble” (verse 23). In Psalm 2:31 we read, “They will come and declare His righteousness to A PEOPLE WHO WILL BE BORN, that He has done this.” Children that are born will have the gospel preached to them. They will learn that Christ “finished the work to save them” so they can be “born again” through faith in Him.

2) They will WORK and EAT: “They shall BUILD HOUSES and inhabit them; they shall PLANT VINEYARDS and EAT THEIR FRUIT” (verse 21). Saints on earth will have “earthly bodies” and they will live in “earthly houses” and eat “food grown on earth,” much like we do now.   (DO)  (504.3)