What did Jesus mean, that the Gates of Hades shall not prevail against his church?
Are not gates used to keep prisoners imprisoned? Whoever would want to break IN to a prison? Only those striving to release the prisoners!
The Gates of Hades keep mankind imprisoned in slavery to the fear of death and to sin. But Jesus Christ declares, "I have the keys of death and Hades!" (Rev. 1:18) Ultimately, once the grave has been emptied on the day of the resurrection, both death and Hades are thrown into the everlasting lake of fire - by Jesus Christ. (Rev. 20:14)
Jesus releases those who were held in slavery by their fear of death" (Heb. 2:14-15). He does this by destroying the one who holds the power of death, the devil. Yet even before the destruction of the devil happens, the Church of Christ is triumphing over the various Gates of Hades, setting the devil's prisoners free. This world is a prison: "The whole world lies under the sway of the wicked one (1 John 5:19). Jesus came to "preach deliverance to the captives" (Luke 4:18) who, like King David, cry out in prayer, "Bring my soul out of prison!" (Psalm 142:7)
In every generation, the Church needs to identify which particular 'gates' are operating on their watch. In the Dark Ages, those were the gates of ignorance and chaining of the Bible, so that the masses of professed Christians hardly had any knowledge of what the Bible would say to them. There were gates of superstition also. Tragically, in this day of education and the Bible being available in thousands of languages, it can still be said that many professed Christians have little knowledge of what the Bible says, and many are still shackled by superstitions.
But in our era we have the gates of materialism, and of secularism, and of individualism, and of populism.
Christians must not spend time shouting to the prisoners beneath the gratings when so many Christians are, themselves, shackled by such things. And so much preaching is nothing more than marching the prisoners around the exercise yard. They are not set free by Christless preaching (2 Tim. 4:1-3). Only Christ's authority causes those wretched gates to yield to his command. Christians use that authority when they unapologetically proclaim the gospel of Christ, though it be "to the Jews a stumbling block, and to Greeks, foolishness" (1 Cor. 1:23). The gospel is the power of God unto salvation. Christ has given his Church weapons which are "mighty in God for pulling down strongholds, casting down arguments and every high thing that exalts itself against the knowledge of God" (2 Cor. 10:4-5).
That's what Christ meant the Church to do, fortified with assurance of his power and protection, and Christ will destroy Hades, with all its myriad gates, on the Day of Judgement.
Source: Rev. Guy R Finnie series of articles in the Portsmouth Baptist Church magazine, 1996