Richard Bauckham, a British New Testament scholar, has argued convincingly that this passage echoes the Old Testament idea of a military census. Israel numbered its tribes to determine the nation's potential military strength. The count was limited to males of military age (Num. 1:3, 19-46; 26:1-51; 2 Sam. 24:1-9, etc.). The 144,000 in Revelation thus consist of males from the 12 tribes of Israel (Rev. 14:4).
The repeated formula "from the tribe of..." particularly echoes the census of Numbers 1 as Israel organized for the conquest of the Promised Land. That census provided the model for the eschatological war in the Dead Sea scrolls (1QM), as well as the book of Revelation. The number of the Israelite army in Revelation 7 is clearly symbolic, as are the dimensions of the New Jerusalem. The 144,000 represents the totality of Israel arrayed in opposition to the forces of evil (Rev. 9:16; 17:14; 19:11-21). In other words, Revelation describes the spiritual issues of the end-time in military terms.
The 2003 invasion of Iraq was the most technologically advanced military engagement in history. With the wonder of stealth technology, cruise missiles, and GPS-guided munitions, it almost seemed as if one could wage battle with the push of a button. But territory is not considered taken until occupied with the very low-tech presence of infantry. They sleep on the ground, carry their own food, and find themselves closest to the fighting. Without their presence land would not change hands--there would just be the destruction of distant targets.
A similar principle appears in the spreading of the gospel today. While mass media and the Internet can play a role in reaching people, it is still the infantry, God's faithful people making disciples one by one, that proves to be the decisive difference. Just as no amount of bombardment can replace the soldier, so no amount of media can substitute for the faithful witness. If you have enlisted in God's infantry, you are irreplaceable. The Lord has commissioned you to go make disciples of the nations. Television and radio can't do that for you.
Lord, I want to make a difference in the real world. Touch my heart with someone's need today.