Matthew 16:6 and 12 are two verses where Jesus warned His disciples of these teachings. They read, “Then Jesus said unto them, Take heed and beware of the leaven of the Pharisees and of the SadduceesThen understood they how that He bade them not beware of the leaven of bread, but of the doctrine of the Pharisees and the Sadducees.”  In short, the answer to your question is that the teachings of the Pharisees and Sadducees were EVIL, which leaven always symbolizes, and if people followed their doctrines they would be lost forever in hell. In Matthew 15:14 Jesus said this about the Pharisees and their followers, “Let them alone: they be blind leaders of the blind, And if the blind lead the blind, both shall fall into the ditch.” One of the most solemn charges the Lord Jesus made against the Pharisees is found in Matthew 23:15, “Woe unto you, scribes and Pharisees, hypocrites! For ye compass sea and land to make one proselyte, and when he is made, ye make him twofold more the child of hell than yourselves.”

Let’s take a closer look at the evil doctrines of the Pharisees and the Sadducees. In Luke 12:1 Jesus said, “Beware ye of the leaven of the Pharisees, which is hypocrisy.” A “hypocrite” is literally “one who wears a mask.” The Pharisees were religious charlatans who PROFESSED TO BE TEACHERS OF THE PEOPLE, but all the while they were, as another has said, “Masters of masquerade.” They taught the people one thing but didn’t follow their own teachings. Because of this Jesus referred to them in Matthew 23 as hypocrites no less than seven times!  Besides being hypocrites, they were guilty of ADDING THEIR TRADITIONS to the Word of God and as a result they REPLACED GOD’S WORD with those traditions. Listen to what Jesus had to say about this in Matthew 15:3 and 9, “Why do ye also transgress the commandment of God by your traditions? But in vain they do worship Me, teaching for doctrines the commandments of men.” As we study the gospels we see that the Pharisees were the greatest enemies of Christ. They rejected the truth that He was the Son of God and eventually they turned Him over to Pontius Pilate to be crucified because He claimed to be the Son of God. Is it any wonder that Jesus warned the people to “Beware ye of the leaven of the Pharisees?” We have modern-day Pharisees occupying pulpits who are guilty of the same evil teachings and thus we too need to be on guard against them and their evil doctrines.

The doctrine of the Sadducees was just as bad, though for different reasons.  Unlike the Pharisees, who were SELF-RIGHTEOUS HYPOCRITES who taught people their traditions instead of God’s Word; the Sadducees were RATIONALISTS who taught the people that there was NO RESURRECTION and thus NO AFTERLIFE. Matthew 22:23 confirms this, for it says “The same day came to Him the Sadducees, which say that there is no resurrection.” If we were to read verses 24-28 we would see them advancing this teaching with a hypothetical story designed to prove that there is no resurrection and life after death. They also DENIED THE EXISTENCE OF ANGELS and SPIRITS of any kind. We read of this in Acts 23:8, “For the Sadducees say that there is no resurrection, neither angel, nor spirit.” This was, in essence, a wholesale denial of a spiritual world, which means THEY DENIED GOD’S WORD and the fundamental truths of Scripture. They were more interested in politics and power instead of religion, much like liberal preachers today who deny miracles, the immortality of the soul, and eternal punishment. Their teachings, like that of the Pharisees, were damnable heresies that were leading people to hell. Again, is it any wonder that Jesus warned the people to “Beware of the leavenof the Sadducees?”  (180.2)  (DO)