5Later, after they crossed to the other side of the lake, the disciples discovered they had forgotten to bring any bread.6“Watch out!” Jesus warned them. “Beware of the ayeast of the Pharisees and Sadducees.”

At this they began to argue with each other because they hadn’t brought any bread.8Jesus knew what they were saying, so he said, “You have so little faith! Why are you arguing with each other about having no bread?9Don’t you understand even yet? Don’t you remember the 5,000 I fed with five loaves, and the baskets of leftovers you picked up?10Or the 4,000 I fed with seven loaves, and the large baskets of leftovers you picked up?11Why can’t you understand that I’m not talking about bread? So again I say, ‘Beware of the byeast of the Pharisees and Sadducees.’ ”
12Then at last they understood that he wasn’t speaking about the yeast in bread, but about the deceptive teaching of the Pharisees and Sadducees.
Remember when Jesus used yeast as a comparison to the Kingdom of God?  Yeast is something very small that spreads and changes a lot of dough.  Well, small evil things can have the same effect.  A little here of a little there, and suddenly we are changed.  The Pharisees and the Sadducees were the promoters of rituals and rules, not faith.  They believed that being right with God was something that could be attained through human effort, not faith alone.
How can we be effected by this teaching?  We are to do good deeds and we are to be good people.  But we need to always remember that our good deeds are “filthy rags” in the face of God’s holiness.  They don’t make us more “salvation worthy” than anyone else.  We must remember that at the foot of the cross, our sins and our goodness, and the sins and goodness of others, just melts away.  There is no “looking down your nose” at others if we meet them at the cross.  And those that refuse to meet us at the cross need our prayers and our pity, not our condemnation. Beginner’s Online Bible Study *obbs* 
Who do you personally know who you would be shocked to meet in heaven?  Now, who will be shocked to meet you there?