1 Finally then, brethren, we request and exhort you in the Lord Jesus, that as you received from us instruction as to how you ought to walk and please God (just as you actually do walk), that you excel still more. 2 For you know what commandments we gave you by the authority of the Lord Jesus. 3 For this is the will of God, your sanctification; that is, that you abstain from sexual immorality; 4 that each of you know how to possess his own vessel in sanctification and honor, 5 not in lustful passion, like the Gentiles who do not know God; 6 and that no man transgress and defraud his brother in the matter because the Lord is the avenger in all these things, just as we also told you before and solemnly warned you. 7 For God has not called us for the purpose of impurity, but in sanctification. 8 So, he who rejects this is not rejecting man but the God who gives His Holy Spirit to you. 1 Thessalonians 4:1-8 (NASB)
Holiness is commanded by God. He wills it. Our Lord Jesus Christ requires it and the Word of God calls for it. The goal of our redemption is that we become Holy as God is Holy. Our Lord died on the cross in order that all of His people would be justified. This justification is God’s declaration that we are righteous having Christ’s righteousness imputed to our account. This had to come first in order that we be sanctified, that is, made Holy.