What did Jesus mean when He condemned the scribes and Pharisees for proselytizing, saying that those converted were ‘twofold more the child of hell than yourselves’ (Matt. 23:15)? Why would the proselyte be a child of hell at all?
In Matthew 23 Jesus is condemning the scribes and Pharisees on numerous points, most of them being their outward show, over-concern about trifles and their neglect of the really important aspects of faith and obedience. Many of the statements He made are, from a literary point of view, hyperboles, or gross exaggerations to make a hard hitting point. Among other things He called the scribes and Pharisees snakes, blind guides, fools, whited sepulchers, hypocrites
When He condemned their methods of proselyting, because of the effect it had on the proselyte himself, Jesus was pointing up the importance of the missionary’s motives and methods in talking to newcomers. The Pharisees were, from Jesus’ point of view, children “of hell,” i.e., fit only to be destroyed themselves. The word translated “hell” in this passage is Gehenna, which was, literally, the garbage dump outside Jerusalem. Jesus was not inferring any connection with any belief in eternal torment. If we were to take His words literally, how could anyone be a “child of hell”? What children could an infernal region produce?
It seems likely that Jesus was condemning the Pharisees for their overweening self-confidence and self-love, which came across to proselytes as a religion empty, void, and valueless. At its best, Judaism in Jesus’ day was a maze of traditions and outward rules which had long since lost sight of the original intent of the law of Moses as given by God.
Jesus’ words are a warning to all would be missionaries that all conversions are not sincere, that an enthusiastic convert can be more bigoted and more blind than the person who converted him, totally missing the heart of true religion. But at the same time Jesus was not discouraging missionary zeal, as His own example taught clearly.