If you don't know what hypocrisy is, it will be difficult for you to beware of it. Too often well meaning, sincere, gullible people want to give everyone including the devil himself the benefit of the doubt. Gullible people think that the hypocrite just made a mistake and they really aren't that bad. Jesus reminds His disciples to maintain a guarded mindset. Luke 12:1-3 teach that whatever is spoken in the dark will be heard in the light, and what has been spoken in the inner rooms will be heard on the housetops. In the midst of numerical success, Jesus deals with subtlety of hypocrisy. Jesus is not concerned with the numbers alone, but He is concerned about the purity among His disciples.
What is a hypocrite? It is one who answers; then, a stage-actor; it was his custom for Greek and Roman actors to speak in large masks with mechanical devices for augmenting the force of the voice; hence the word becomes used metaphorically for dissembler, a hypocrite. Our Lord spoke of this some 15 times in Matthew, Mark and Luke. We must acknowledge that the pharisees of the Bible are represented today among people with insincere attitudes that seek to represent God. These people represent the broad way that leadeth to destruction (Matthew 7:13). God's people who seek to uphold his ways in purity and holiness cannot participate in mixed messages. Saints, as well as the world, need to see the beautiful bride of Christ (His Church). We must see without spot or blemish (Ephesians 5:27).
'Leaven' represents corruption, defilement, pollution and that which is watered down. Our Lord cautions us that this is the way the beguiler works. He wants the Church of Christ to become impotent or powerless. Satan knows he can affect the church this way, if we lower our standards to that of the world. Jesus loves us better than we love ourselves and HE WARNS US! Will we heed to His warning? Will we choose to be like Eve and tune God out to do our own thing? Satan is always so smooth! It is easy to give in to him, if we let our guard down. So church, beware of hypocrisy as it can be observed in others; most of all, beware of the hypocrisy in ourselves. God bless you.