For this is the will of God, your sanctification: that you should abstain from sexual immorality, that each one of you should know how to possess his own vessel in sanctification and honor, 1 Thessalonians 4:3-4 MEV
What is sanctification exactly? The biblical definition is: to be set apart to God and His service.
This requires that the one sanctified leave his or her old life and live a life of purity, honor, and sacrifice as enabled by the Holy Spirit.
The shed blood of Jesus, cleanses us and delivers us from the bondage of sin, the fear of death, and the fear of man. Our verses today go on to say,
not in the lust of depravity, even as the Gentiles who do not know God, and that no man take advantage of and defraud his brother in any matter, because the Lord is the avenger in all these things, as we also have forewarned you and testified. For God has not called us to uncleanness, but to holiness. 1 Thessalonians 4:5-7 MEV
The call to live holy could not be more clear.