The teaching of the Pharisees and Saducees is compared to yeast in that yeast rises and make the bread or dough bigger, it expands. The Pharisees teaching spreads across to many people and expands but the teachings are not correct because they worship God with they lips and not from their hearts.

They had to have a sign from heaven to believe everything that Jesus says. Jesus said to beware of they teaching because it was false and would lead the people the wrong way.

In the text given for this lesson, Jesus thought that the disciples had not fully understand who He was, therefore it would not be wise of them to go out and preach or proclaim the name of Jesus. To tell someone about a person or about anything you need to know fully what you are talking about.

Maybe Jesus knew how the pharisees especially tried to trap Him or look at everything He did in a different manner, always opposing so He did not want to put the disciples through the same thing.

After His resurrection, He again told the disciples not to say anything about Him this was because it was not yet His time.

We have to fully understand who Christ is in order to tell others of Him.