Sanctify God in Your Heart
Peter's text expresses the fundamental nature of discipleship. The term sanctify (hagiazo) is defined by Arndt and Gingrich as "treat as holy, reverence." Thayer states "to render or acknowledge to be venerable, to hallow." The Lord God is to be enthroned in our heart. Such veneration is logical, as He is Lord. A failure to reverence Him is a failure in discipleship.
The text is very similar to a passage found in the book of Isaiah. The King James version renders Isaiah 8:13, "Sanctify the LORD of hosts himself; and let him be your fear, and let him be your dread." A contrast is here made between men and God. God is the one to be feared. He is the one we are to concern ourselves with, rather than men. The Christian ought never to make decisions based upon what men think. Rather, our sole concern should be to please God. Jesus said, "And do not fear those who kill the body but cannot kill the soul. But rather fear Him who is able to destroy both soul and body in hell" (Matthew 10:28).
Leviticus 19 serves to establish what God expects of man, and why. Note the following examples:
God requires us to live lives of righteousness, submitting ourselves to His will. This is required of us because He is "the LORD." Remember Peter's statement in 1 Peter 1:15-16, "But as He who called you is holy, you also be holy in all your conduct, because it is written, 'Be holy, for I am holy.'"
Here is the lesson: In order for us to truly sanctify God in our hearts, we must live consecrated lives. This truth is established time and again in the New Testament. In 1 Corinthians 6 Paul wrote of the past conduct of some of the Christians in that city. He wrote of fornication, idolatry, homosexuality, thievery and drunkenness. Concerning those characterized by ungodliness, Paul wrote in verse 11, "And such were some of you. But you were washed, but you were sanctified, but you were justified in the name of the Lord Jesus and by the Spirit of our God."
As we are "sanctified in Christ Jesus, called to be saints," (cf. 1 Corinthians 1:2), we must put off sinful practices, and live lives of holiness before Him.
Paul stated it clearly to the Thessalonians.
God desires that we be holy and righteous in our life. When he called us, (remember, sanctify basically means to consecrate or set apart), he did not intend for us to live as does the world. The calling of God is of a higher order and requires moral, ethical and doctrinal purity. In this specific context, we are to "abstain from sexual immorality," but the principle applies equally in every facet of our lives before God.
As Christians we will be tempted to compromise our calling. A lowering of standards is unacceptable. Remember, we must hallow God in our hearts. Paul wrote:
"Therefore if anyone cleanses himself from the latter [in this context, false doctrine], he will be a vessel for honor, sanctified and useful for the Master, prepared for every good work. Flee also youthful lusts; but pursue righteousness, faith, love, peace with those who call on the Lord out of a pure heart" (2 Tim. 2:21-22)
We are sanctified (called out) to live holy (sanctified) lives. This we must do if we are truly venerating (sanctifying) the Lord God in our hearts.