Beware of the Leaven of the Pharisees and Sadducees

The first time he uses that phrase is in Matthew chapter six when he says, look, God cares about the birds in the field. And then of course Jesus is saying, beware of the leaven of the Pharisees and Sadducees. Now some people have argued that this is a clear sign that Matthew doesn't know the first century Jewish world. This is not anything like that. No, Matthew's not showing ignorance of the differences between the beliefs of the Pharisinges and Sad DUcees. The problem is neither can read the signs of the times because neither understand who Jesus is.