What the Bible says about Forces of Evil
(From Forerunner Commentary)
The church has misunderstood this verse. Its dominant interpretation has been that Greek hades always refers to “the grave.” This understanding is incorrect in this case.
What Christ describes in this verse is an active, military-style engagement—a spiritual war between the church and its enemies. Since a grave is merely a receptacle for a dead body, it does not—cannot—make war. Jesus' phrase, “gates of Hades,” which Matthew correctly remembered and recorded for us, is a metaphorical expression describing the forces of evil: Satan and his horde of demons. They, not the grave, make war against the church. Christ asserts that the demonic forces of evil will not triumph over His church.
Jesus pictures His church—His spiritual Body—as dominating the warfare between it and the Adversary and his minions. We can be assured that Christ has already defeated Satan, as shown in the encounter recorded in Matthew 4 and Luke 4, and in His resurrection and ascension to His Father's right hand in heaven. We will be saved by His continuing life (Romans 5:10).
Those of His faithful brethren, the elect, have nothing to fear about His willingness and His ability to overcome Satan on our behalf. Knowing that the church, with Him as its Head, is on the offensive ought to be faith-building.
John W. Ritenbaugh
A Truth About Revelation 2 and 3