Matthew 23:15
Woe to you, scribes and Pharisees, hypocrites! For you travel across sea and land to make a single proselyte, and when he becomes a proselyte, you make him twice as much a child of hell as yourselves. The third woe: the missionary zeal that produces converts who are twice as much a child of hell as the converts' teachers. The problem is not the proselytizing but what the convert is converted to — the Pharisaic system that closes the kingdom rather than opens it.