Romans 2:24 : For the name of God is blasphemed among the Gentiles because of you, even as it is written. The Jews sought to make proselytes. Jesus said they would compass sea and land to make one proselyte. They might have had great success, if they had lived up to their preaching. It is hard to make any one believe there is any good in your doctrine, if it has not done you any good. The Jews had so lived as to cause the Gentiles to blaspheme their preaching in-stead of believing it. The Jews had become a hiss and a byword. Read Isaiah 52:5.
The greatest hindrance to the spread of the gospel today is the conduct of many of its professed believers. Immorality, worldly-mindedness, dishonest dealing, and divisions hinder Christianity. Opposition from without is not what hurts the most. The right kind of living on the part of professed Christians gives them a favorable hearing when they present the gospel. Do not try to sell the gospel by mere talk; show them a sample of what the gospel will do for the people who really believe it. You will then likely make a believer instead of a blasphemer. "Even so let your light shine before men; that they may see your good works, and glorify your Father who is in heaven" (Matthew 6:16).