The 144,000 are first mentioned in Revelation 7, “And I heard the number of them which were sealed: and there were sealed an hundred and forty and four thousand of all the tribes of the children of Israel.” Revelation 7:4
This passage comes in an interlude between the judgment of the sixth seal of the tribulation (Revelation 6:12–17) and the opening of the seventh seal (Revelation 8:1).
How one answers the question depends on which interpretive approach one takes to the book of Revelation. The futurist approach, which is considered the best, interprets the 144,000 literally. When taken at face value, Revelation 7:4 speaks of 144,000 actual people living during the end-times tribulation. Nothing in the passage leads to interpreting the 144,000 as anything but a literal number of Jews—12,000 taken from every tribe of the children of Israel, according to verses 5–8.
These 144,000 Jews are “sealed,” which means they have the special protection of God and are kept safe from the divine judgments and from the wrath of the Antichrist during the tribulation. They can freely perform their mission to minister to the lost during the the tribulation. Their presence is a testimony that God will not give up on mankind even during the tribulation by providing these evangelist in the heart of the plagued period.
It had been previously prophesied that Israel would repent and turn back to God (Zechariah 12:10; Romans 11:25–27), and the 144,000 Jews are a sort of “first fruits” (Revelation 14:4) of that redeemed Israel. Their mission is to evangelize the post-rapture world and proclaim the gospel during the tribulation period. As a result of their ministry, millions—“a great multitude that no one could count, from every nation, tribe, people and language” (Revelation 7:9)—will come to faith in Christ.
Much of the confusion regarding the 144,000 is a result of the false doctrine of the Jehovah’s Witnesses. The Jehovah’s Witnesses claim that 144,000 is a limit to the number of people who will reign with Christ in heaven and spend eternity with God. The 144,000 have what the Jehovah’s Witnesses call the “heavenly hope.” Those who are not among the 144,000 will enjoy what they call the “earthly hope”—a paradise on earth ruled by Christ and the 144,000. It is true that there will be people ruling in the millennium with Christ. These people will be comprised of the church (believers in Jesus Christ, 1 Corinthians 6:2), Old Testament saints (believers who died before Christ’s first advent, Daniel 7:27), and tribulation saints (those who accept Christ during the tribulation, Revelation 20:4). Yet the Bible places no numerical limit on this group of people. Furthermore, the millennium is different from the eternal state, which will be established at the completion of the millennial period. At that time, God will dwell with man in the New Jerusalem. He will be our God, and we will be His people (Revelation 21:3). The inheritance promised to us in Christ and sealed by the Holy Spirit (Ephesians 1:13–14) will become ours, and we will be co-heirs with Christ (Romans 8:17).