Question: "Why does it say in 1 Timothy 4:1 that some will depart from the faith?"
Answer: As part of Paul’s instructions for preparing Timothy to lead and appoint leaders in the church at Ephesus, Paul warns him that some will depart from the faith: “Now the Spirit expressly says that in later times some will depart from the faith by devoting themselves to deceitful spirits and teachings of demons, through the insincerity of liars whose consciences are seared” (1 Timothy 4:1–2, ESV).
Paul uses the Greek word apostesontai, which means “to be apart from, depart from, or stand apart from.” It’s the source of our English word apostasy. In this case, those departing are leaving “the faith.” Instead of holding to the sound teaching that is part of the faith that is in Christ Jesus (as Paul mentions in 1 Timothy 3:13), these people are choosing to follow a different path and listen to different voices.
Those who depart from the faith in the last times will choose to listen to deceitful spirits and doctrines or teachings of demons. They will follow false teaching that sounds convincing and is intended to deceive. These falsehoods are carefully devised; their design is to deceive people from following the faith. Those who depart from the faith are following liars with “seared” consciences. Their consciences are burned; the false teachers, who are mouthpieces for evil spirits, are dull to their own hypocrisy and unscrupulous behavior (1 Timothy 4:2).
To ensure that Timothy understands, Paul provides him with a couple of specific examples. The false teachers of the last times will forbid marriage and abstain from foods that God has permitted (1 Timothy 4:3). Those who will depart from the faith will be deceived by a kind of legalism. No longer will these people focus on the grace of Christ or the faith that Jesus authored and perfected (Hebrews 12:1). Instead, they will attempt to regulate behavior in contradiction to the freedom God has provided.
In the immediate context, Paul explains how some people will depart from the faith, but not exactly why. However, in 1 Timothy 6:3–5 Paul offers an explanation of why a person might choose to follow falsehood. Paul notes that one either agrees with the “sound instruction” of Christ or becomes “conceited and understand[s] nothing.” A teaching that differs from the apostle’s doctrine does not comport with godliness (1 Timothy 6:3). Paul further explains that these who depart from the faith have an unhealthy interest in controversies and disputes (1 Timothy 6:4). The result is envy, strife, abusive language, evil suspicions, and constant friction. Such is the condition of those who are depraved of mind and deprived of truth (1 Timothy 6:4–5).
The warning, then, is that we ought to hold fast to the sound words—the words of Jesus Christ. Paul cautions Timothy to “watch your life and doctrine closely. Persevere in them” (1 Timothy 4:16). Before Timothy could encourage others to hold fast to the faith, he needed to guard himself against hypocrisy. Only then could he teach well and encourage others not to depart from the faith. Despite all efforts, some people will depart from the faith, and Timothy ought to carefully prepare to deal with such people. The preparation involved being above reproach himself and being equipped with the sound words of Christ and grounded in the teachings of the faith.