We are constantly surrounded by things that would kill us if they could. There are many creatures and organisms that are deadly to us if they attack us. There are chemicals and substances all around us that are potentially fatal. The world’s most deadly toxin, according to many scientists, is so poisonous that just one nanogram per kilogram of body weight is enough to kill a person. For this reason, we take reasonable precautions to protect ourselves. We cook our food to kill any potential germs that would make us sick. We wear bug spray to keep parasites from attacking us. Most of us do not go swimming with sharks. We are very good at protecting our bodies from things that would harm us. But what about our souls? Are we careful to guard against things that are potentially harmful to our souls? In Matthew 16, Jesus warned His disciples to be on guard against the evil influences that surrounded them. The language He used, however, left them wondering what He really meant. He said, “Take heed and beware of the leaven of the Pharisees and of the Sadducees.” They thought at first that He might have been referring to real food. But what Jesus was really talking about was the teachings of the scribes and Pharisees. Their false doctrine was like leaven because just a small amount would permeate a large loaf. We cannot afford to let our guard down when it comes to false doctrine. Any belief that contradicts scripture must be avoided at all cost, because it will eventually taint many other beliefs and behaviors.