“No good tree bears bad fruit, nor does a bad tree bear good fruit. Each tree is recognized by its own fruit. People do not pick figs from thorn bushes, or grapes from briars. The good man brings good things out of the good stored up in his heart, and the evil man brings evil things out of the evil stored up in his heart. For out of the abundance of the heart his mouth speaks.”
Luke 6: 43-45
One expression I’ve heard a number of times and really appreciate is: “A fish doesn’t swim in order to become a fish. It swims because it is a fish.” Fish swim simply because it is inherent in their biological makeup; it is in their nature to do so. This is essentially what Jesus says in these verses. Good trees don’t produce good fruit in order to become good trees. They produce good fruit because they are good trees. Grapevines produce grapes because they are grapevines.
The point Jesus makes is that we do what is in our nature to do. Good works aren’t simply about adhering to a written code. Good works are the result of a “good” nature.
But we aren’t good (Romans 3:10). And while we may be able to comply with a written set of laws, it cannot change our natural desire to do evil. Jesus made this point in Matthew 5 in the examples of murder and adultery. You might abstain from committing those acts, but that doesn’t fix the sinful nature that still wants to hate and lust.
So, what is the answer? The answer is that God, through the indwelling of the Holy Spirit must miraculously change our nature from one that is hostile against Him, to a new nature that desires to follow and obey Him. The same Holy Spirit that saved us regenerates us. That’s what “Born Again” means. Now with the new God nature living in us makes it possible for us to be good people who bring forth good things from our hearts.
So how does our fruit taste? Changing our nature from the old sinful nature to a new godly nature is entirely the work of the Holy Spirit. However, Paul admonishes us in 2 Corinthians 13:5, “Examine yourselves to see whether you are in the faith.” And Peter tells us to make our calling and election sure (2Peter 1:10).
Even so, we don’t do this self-examination to become followers of Christ; we do this because we are followers of Christ…if indeed we are followers of Christ