The false teaching is that Jesus taught tithing in Matthew 23:23 which, they say, is clearly in the New Testament.
The problem here is the arbitrary division of our Bible. The New Covenant did not begin at the birth of Jesus, but at his death. Tithing is not taught to the church after Calvary! When Jesus discussed tithing in Matthew 23:23, he was only commanding obedience to the Old Covenant Law which he endorsed and supported until Calvary. In Matthew 23:2, 3 Jesus told his followers to obey the scribes and Pharisees "because they sit in Moses’ seat." There is not a single New Testament Bible text which teaches tithing after Calvary – period!