Leviticus 11:44-45 For I am the Lord your God: ye shall sanctify yourselves, and ye shall be holy; for I am holy; neither shall ye defile yourselves with any manner of creeping thing that creepeth upon the earth. For I am the Lord that brings the you up out of the land Egypt, to be your God: ye shall be holy, for I am holy.
The Torah generally, and Leviticus in particular, emphasizes the holiness of God. The Book leaves no doubt that God is HOLY! And if any sinful human approaches the Lord, he must be ritually clean, purified, washed of sin, and holy. And the Lord leaves no doubt as to what is clean and holy and what is not. There can be no leper in the camp, or mold, no dead bodies, and nothing unclean can be eaten, etc. In this chapter God gives extensive details about what is clean and unclean.
Why? Because God is HOLY. Get the point. And God will not tolerate anything in His presence that is unclean, impure, or unholy. But He wants you, and therefore He must make you holy. And this He did, by giving His Son to shed His blood and by sending the Spirit to bring you to faith in Christ. Once you receive Christ and believe that message you are declared holy and righteous, justified by faith. Then for the rest of your earthly life He sent the Spirit to bring your daily life more in line with your declared state.
Faith, then, is the response. We believe God is Holy; I am not; we believe the Son died and rose to earn God’s righteousness; and we believe that the Spirit is leading me into a more holy lifestyle. In this way, the command and predicted promise comes true: you shall be holy. By faith, we are. By life, we are getting there. We cannot reach holiness and perfection in this life, but we do respond by getting closer.