Either definition can be used to describe some Christians and churches today. Some have been “pushed” into the world’s way of thinking by outside forces (parents, professors/teachers, movies, T.V., music, etc.). Without a solid pattern of Christ in their lives, these people easily conform to faulty thinking and behavior for simply “not knowing any better.”
Others have allowed a decaying of their Christianity to occur from living unhealthy spiritual lives. Lack of consistent study in the Bible and of a prayer life, unhealthy relationships all shut off the Holy Spirit’s teaching, directing, and empowering them to build and grow in Christ. Hence, their inner structures are vulnerable to rot, decay and the moldiness of the world’s philosophies. 1 Timothy 3:16 assures us that, “All Scripture is God-breathed and is useful for teaching, rebuking, correcting and training in righteousness, so that the man of God may be thoroughly equipped for every good work.” Without these as constants in our lives we may miss the errors of our ways. Our wrong thinking, believing, behaving will continue without the aid of rebuke, or correction, much less the on-going training needed.
Have you wondered why many Christians are so accepting of worldliness? Or so easily caught up in sexual immorality, liberal philosophy, materialism and the like? They have probably become “moldy” in their Christian lives. If they do not understand their faith in Christ, then they have no means for standing against the “fiery trials” (1 Peter 4:12) or the “wily schemes of the devil (Ephesians 6:11).
Are we prepared to be serious in the war against the mold that is creeping into and growing in the lives of our young and old alike? Are we giving them the knowledge and tools to break the ungodly molds of this world to break free and be transformed in Christ? Only then will we see the spiritual resolve to resist, to stand firm and to inform our lost and dying world with the truth of the gospel of Jesus Christ. Without this our churches will continue to be lukewarm and feeble, and our nation will continue to fail.
In the structure of a house, mold and mildew (fungus) must be removed, cleaned out and eliminated or the structure will soon collapse. It is time to begin anew. It is time to fight back with God’s truth. It is time to begin a new and strong plan for teaching, rebuking, correcting and training in righteousness. Start in the Nursery and work it through all ages, even to your senior citizens. Do not bypass anyone. Make your church the neighborhood Bible School and Seminary for teaching and training to instruct for change and real Christ-likeness. Measure all teaching by God’s Word, the Holy Bible, and none other. It must be the standard.
Give your people the tools they need. Trust them to be able to think and to understand even the deep, meaty things of God.
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 Merriam-Webster, Inc. 2022