Comment: Smith’s Bible Dictionary explains that  proselyte is “the name given by the Jews to foreigners who adopted the Jewish religion”. In his commentary, Adam Clarke says that to “compass sea and land” is “A proverbial expression” like saying “You leave no stone unturned”.  He said the Pharisees and scribes “did all in their power to gain converts, not to God, but to their sect”. In the days of King Ahasuerus when the plot of Haman turned against him the Bible record has it that “…many of the people of the land became Jews; for the fear of the Jews fell upon them”. (Esther 8:17) Both on that famous day of Pentecost and at the time Paul and Barnabas preached at Antioch (in Pisidia) both the natural Jews and the proselytes came to hear the word of God. – Acts 2:10; 13:43.

The point our Saviour  is making is that after people had been converted to the true faith, the leaders by their false teachings and bad examples made these converts to commit greater iniquities than they did before their conversion. (Matthew 15:1-9)  Thus even the things these converts were afraid to do previously because they knew such things were wrong, they now did them brazenly or openly.  Those who have come to Christ should not allow anyone to influence them to sin. See Galatians 1:8, 9; Philippians 2:12.