By way of introduction into Matthew 16, the Pharisees and Sadducees, traditionally bitter enemies of each other, now joined forces together against the Savior.  An issue came up with disciples who forgot to bring along some bread to eat.   Jesus takes this opportunity to teach his disciples.  Matthew 16:6 “Then Jesus said unto them, Take heed and beware of the leaven of the Pharisees and of the Sadducees.”  Here the Master warns against the evil doctrines of the Pharisees and Sadducees.  He compares their doctrines to leaven (yeast) which is put in bread dough to make it rise.  Yeast feeds on the sugars present and as it passes through the flour, it causes it to ferment or swell through a gas by-product.   As the leaven works its way through the entire lump of dough, it influences everything.  So also, with these hypocritical Jewish leaders, who are influencing and corrupting everything in Jewish society. 

As a side note: I have heard a couple members of the LDS quorum of apostles make the mistake of referring to leaven as being a good thing.  As in – Mormons – like leaven – being compared to salt and light.  But Jesus and His apostles described sin as leaven.  

Now we come to a very important conversation Jesus has with his disciples.  Verse 13 “When Jesus came into the coasts of Caesarea Philippi, he asked his disciples, saying, Whom do men say that I the Son of man am?”   Who do people say, He is?  Verse 14 “And they said, Some say that thou art John the Baptist: some, Elias; and others, Jeremias, or one of the prophets.”  Some people speculated it was Elijah or Jeremiah or the other prophets that were supposed to return.  We notice that the disciples did