In Exodus 20, the Ten Commandments were given to the children of Israel. They were meant to be followed as God's moral directive for the people who were to represent the one true God among the nations. This revelation set them apart. They were to be as "a city that is set on a hill," which cannot be hidden, full of light (Matthew 5:14). They were called to be holy as God's people. This call to holiness permeates in the book of Leviticus. It is represented in the detailed description of the sacrifices, the cleanliness laws, and the feasts. But it is also directly commanded. Israel was to be holy, even as the Lord is holy (Leviticus 11:44). This commandment towards holiness is later repeated: “Sanctify yourselves therefore and be ye holy: for I am the LORD thy God. And ye shall keep my statutes and do them: I am the LORD which sanctify you (Leviticus 20:7-8).”
Just prior to this commandment in chapter 20, the children are commanded not to worship a false god, nor to look the other way when fellow Israelites turn to worship those false deities. This break from God deserved death at the hands of the community. It was understood that once sinful behavior and false worship had been deemed acceptable by inaction, it would spread like a disease. One's unholy actions could lead others to break covenant. Neither were the Israelites to seek out mediums or those who said to have contact with the dead. When they were in the Promised Land or wherever they found themselves, they were to be holy and rely completely on the Lord. Therefore, God command them to sanctify themselves and be holy.
Holiness has two parts. The first is separation from the common for a special purpose. The second is following God's ethical standard as based on His nature. Most Christians easily recognize the first point because we are all saints, as part of God's people. But to be holy is more than the mere declaration. It is followed with right moral actions and the true worship of the Lord. The reason for this call of separation in standing and action was because of the covenant relationship the children of Israel had with Him, even as we do today, being grafted in through Christ. He is OUR God! Because of this relationship, we are sanctified. Any holiness we have or display is derived from Him.
However, we are fallen and sinful. In our flesh, we desire to run from God toward every false deity and do every detestable thing. But because of His great mercy and grace, we have a relationship with Him and are able to put on true holiness (Ephesians 4:24). He is the one who sanctifies us. He is the one who has given us new desires and the ability to perform good works.
Sometimes, though, we can lose sight of this relationship and the call to holiness. We can start moving towards a false idol and reason with ourselves that certain actions are okay. We must never forget what He has done for us nor our relationship with Him. Though we struggle with our sin nature in this life, let us all run our race seeking to be holy as He is holy, showing the world who should be worshipped. Let us all be the city on the hill. And when we see a brother or sister moving away or struggling, let us show our new holy nature by being a strong arm to those who are week. Let us all represent the Lord.
Soli Deo Gloria