This section is clearly related to the material in chapter 13. There is a contrast between those who have taken the mark of the beast in chapter 13 and the 144,000 witnesses (who were introduced in chapter 7.) Note that these witnesses have the name of God on their foreheads, in contrast to the followers of the beast, who have the name of the beast on their foreheads.
The description of the 144,000 is quite impressive. The descriptions of these men indicate that they are purified for God’s service. First, they have not “defiled themselves.” The verb μολύνω in the LXX describes a person who has done something that makes them ritually unclean (touching blood (Lam 14:4), eating impure foods (Isa 65:5), or sexual activity (Zech 14:2). But the word was also used for the defilement of the temple, (1 Macc 1:37; 2 Macc 6:2). “Kept pure” in the NIV is literally “they are virgins” (as in the KJV), and the word is highlighted by the fact that they have not defiled themselves with women. The Greek word for virgin (παρθένος) is normally used for a young woman, not a young man.
It is possible to take this term literally as a reference to men who have chosen to remain celibate because of their service to God. Both the priest and the soldier were exclusively male in the Old Testament. This could be taken as general service, like a priest during his time of service (Lev 15:18). Or, this could be taken as a reference to Holy War. There are several places in the Old Testament were men abstain from sexual activity while engaged in a Holy War (Lev 15:16, Deut. 23:9-10). The reasoning for this is unclear, although have unmarried men as soldiers makes good sense, the less family waiting behind the better, the men will be more apt to sacrifice themselves if there is no wife and kids at home. This makes some sense in our context since the young men are fighting something of a holy war, and any family relationships might hinder their boldness in resisting the power of the beast.
Second, the 144,000 “follow the Lamb wherever he goes.” The language of “following” Christ is almost completely limited to the Gospels. Following in the Gospels does not mean “accepting the teachings of” the one you follow. (For example, “Pastor Smith followed N. T. Wright in his teaching on sanctification.” The “following” is intellectual.) Following Christ is to become his disciple on a much more intimate level, and to accept a commitment to continue following Christ even to death. There are many passages that talk about the disciple’s willingness to give up earthly pleasure and security in order to follow Christ on the deepest level possible. The other unusual thing about this description is that the Lamb is portrayed as a shepherd (as in 7:17). This is to be expected since the Messiah’s leadership is described as a “shepherd” in Is 40:11 and Ezekiel 34:23.
Third, the 144,000 “were purchased from among men and offered as firstfruits to God and the Lamb.”The martyrdom motif continues in the next description. “Offered as a firstfruit” is a clear reference to sacrifice. Firstfruit refers to the practice of sacrificing the first portion of a crop to the Lord, or the best of ones flock to the Lord. The Old Testament is very clear that the only acceptable sacrifice is the best sacrifice; therefore the flawless firstborn male lamb is the most pleasing sacrifice to the Lord. Chapter 14 will eventually describe a harvest, perhaps there is an intentional linking of the 144,000 with that harvest. The 144,000 are the firstfruits of men, which might mean that they are the best that men have to offer to God. The problem is that God is not accepting these men as human sacrifices. The meaning might better be that they are the firstfruits of the harvest of the redeemed, the first to be protected in the tribulation period, or perhaps the first set aside to God at the beginning of the period.
Fourth, “no lie was found in their mouths; they are blameless.” This description concerns moral purity, and continues the theme of describing the 144,000 as spotless sacrifices. The phrase is used in Zeph. 3:13 to describe the remnant of Israel in the last days.
The whole scene in heaven is designed to give comfort to the reader; those that have been set aside to the Lord in the tribulation are being brought through and will stand with the Lamb in Zion, and will apparently rule with him in the Kingdom. After the description of the protection of the 144,000, John describes three angelic messengers that continue the theme of comfort and hope.