I have often puzzled over many of the purity laws God gave to Israel. Some of them seem connected to physical health issues, such as how to handle Leprosy or bodily discharges. But some of the animals considered "detestable" or "unclean" do not seem to be stem from the same sort of issue. There is nothing inherently dirty about these animals that makes them inedible. In fact, the New Testament considers these unclean or detestable animals acceptable. As far as I know, a pig is till a pig, and a catfish is still a catfish. It does not seem to be connected to health benefits because many people who eat these animals sometimes live extremely long lives.
The only principle that I can find that ties all of these together has little to do with health benefits, germs, and other such things. Obviously, health benefits applies to some of them but not all of them. When I consider that the end of a period of a person being rendered unclean usually involves some sort of interaction with a priest, a sacrifice, and blood, which is sometimes sprinkled on the formerly unclean person, it tells me that this is not a matter of physical health, but of holiness and inner purity. As a whole, these purity laws seem to be designed to set apart God’s people as a holy people and to teach them to remain pure.
These instructions demonstrate that there were so many, many things in life that could make one impure that the Israelite needed to be aware of them in order to avoid them. Becoming impure was not just an individual issue. Impurity could spread from one object/person to another. It could affect a person’s family, neighbors, and the entire community. Impurity cut a person off from the community and from God. Therefore, the Israelite also needed to know God’s instructions on how to be purified in the case of accidental contact and be restored to the community and to God.
Our list today of what is impure and can defile us today as Christians is much more narrow than the list given to Israel. However, this does not mean defilement is any less serious. Jesus said that it is the pure in heart who will see God (Mt 5:8). If impurity is allowed in, it defiles not the body, but the heart and the mind (Tit 1:5). A defiled heart will not and cannot draw near to God. In fact, a defiled heart may not even be aware of being defiled! 1 Timothy 4:2 speaks of those who have a seared conscience. The idea is that the conscience no longer feels, and therefore no longer functions the way it is supposed to. This is how the defilement of sin affects the heart. The most serious consequence of all is that impurity affects one’s relationship with the pure and holy God, and therefore one’s relationship with the church.
There is a clear New Testament example of this. In dealing with sin in the Corinthian church, Paul asked, “Do you not know that a little leaven leavens the whole lump?” (1 Cor 5:6). Just as impurity could spread in the camp, so impurity can also spread in the church. So he went on to write, “Cleanse out the old leaven that you may be a new lump, as you really are unleavened” (1 Cor 5:7). Paul is referring to the unrepentant sinner in the church. Earlier in the chapter he instructed the church to withdraw from the unrepentant sinner using very strong language: “deliver this man to Satan…” The purpose was not only to motivate this person to repent and become pure again, but also to keep sin from spreading in the body. He explained, “I wrote to you in my letter not to associate with sexually immoral people— not at all meaning the sexually immoral of this world, or the greedy and swindlers, or idolaters, since then you would need to go out of the world. But now I am writing to you not to associate with anyone who bears the name of brother if he is guilty of sexual immorality or greed, or is an idolater, reviler, drunkard, or swindler—not even to eat with such a one” (1 Cor 5:9-11).
Jesus taught about a much more subtle form of defilement. We think of what we see, listen to, and engage in as being the things that defile us. This is true, but Jesus warns us that what comes out of our mouths can also defile us.
"And he called the people to him and said to them, 'Hear and understand: it is not what goes into the mouth that defiles a person, but what comes out of the mouth; this defiles a person.' Then the disciples came and said to him, 'Do you know that the Pharisees were offended when they heard this saying?' He answered, 'Every plant that my heavenly Father has not planted will be rooted up. Let them alone; they are blind guides. And if the blind lead the blind, both will fall into a pit.” But Peter said to him, 'Explain the parable to us.' And he said, 'Are you also still without understanding? Do you not see that whatever goes into the mouth passes into the stomach and is expelled? But what comes out of the mouth proceeds from the heart, and this defiles a person. For out of the heart come evil thoughts, murder, adultery, sexual immorality, theft, false witness, slander. These are what defile a person. But to eat with unwashed hands does not defile anyone' " (Mt 15:10-20).
No wonder the Bible teaches us to guard our heart (Prov 4:23)! No wonder the Bible instructs us to season our speech with salt so that we can give grace with our lips (Phil 4:6)!
The old purity laws have a very important and timeless lesson for us. Since the law is our schoolmaster, the question to ask in reading these purity laws is this: What do they teach us? Even though the Levitical purity laws do not apply to us, they teach us some very important truths about purity and holiness. There are still many, many things that can defile the Christian mind and heart. This is a reminder to be vigilant of those things. If we discover defilement in our hearts, the question to ask is whether we will take the steps for purification without delay. Impurity never stays the same. Unchecked, it always grows and takes over. Being swept under a rug and hoping it will go away only causes it to grow and become more deeply entrenched. Instead of going to a priest, Christians are instructed to confess their sins one to another and pray for each other. All of us are priests and Jesus is our High Priest. We are instructed to boldly approach the throne of grace through Jesus, our High Priest, to find grace to help in time of need. The result of approaching our Lord is that his blood cleanses our conscience and renews us.