False teaching and counterfeit Christianity
Those who are trained in anti-counterfeiting measures don’t focus their training on studying fake bank notes. Instead they spend huge amounts of time studying the real thing: They become so familiar with every detail of the real article so that when they come across a fake or counterfeit bank note they can spot it easily, regardless of how clever the counterfeiters are! The more intimately aware you are of a genuine article the easier it is to recognise a fake. Similarly with us: If we will invest the time in God’s Word, so that we come to know it thoroughly, we will be able to spot false teaching and counterfeit Christianity easily.
Source: adapted from Henry Blackaby, Experiencing God, p.151