The world is full of counterfeits. And we need to be careful to distinguish them from the real thing. There are people who try to fool us. And sometimes we end up trying to fool ourselves. And sometimes we end up being fooled by others because we want to be fooled. Among the things commonly and systematically counterfeited is the gospel. Now water is a simple thing. If you try, you can destroy it by breaking it up into its component parts of oxygen and hydrogen. But the easiest way to mess it up is to add something to it. In the same way, the gospel is a simple thing. And the easiest way to mess it up is to add something to it.
The context of the gospel is that we are all sinners (Romans 3:23; Jeremiah 17:9; Isaiah 64:6) and cannot save ourselves (Romans 7:14; 8:8; John 15:5). To remedy this, God became a Man (John 1:1-18; Philippians 2:5-11; Hebrews 2:9-18) to pay the price for our sins (1 Peter 2:24,25; Colossians 2:13,14; 2 Corinthians 5:21) and validated this by rising from the dead (1 Corinthians 15:1-11; Romans 1:4; 4:25). As a result, Christ offers salvation to those who put their faith in Him (Romans 4:4,5; Ephesians 2:8,9; Philippians 3:9). Now this is a personal faith in Christ as a Person who came to personally rescue me from sin. It is not a set of facts I memorize or a set of rules I follow or an organization I am a part of or some new self-help program I adopt. And if I mix any of these into the gospel, I distort it, and I am in danger of losing it. Because when I add something to the gospel, it adds something I do to what Christ has done, and I am no longer trusting in Him but in my own abilities (Titus 3:5,6; Galatians 2:21; Romans 11:6).
But all this is grounded on the idea that the gospel is based on the truth of God’s Word and is unchangeable (Galatians 1:8,9; Jude 3; 2 Corinthians 11:1-4). We cannot put our trust in other human beings or their organizations (Galatians 1:10; 2:11-16; Proverbs 29:25), but must come to God directly through Christ (1 Timothy 2:5; John 14:6; Acts 4:12). For one of the first steps in undermining the gospel is undermining the authority of Scripture. People may do this by trying to get us to trust in their organization or in their tradition or in their new revelation. The best way to distort the gospel is to add something to it, and the best way to accomplish that is to add something to Scripture. Therefore, we need to stand firm against all additions so that we may maintain the pure gospel, for that is what we truly need.