Leviticus 20:7-8 Sanctify yourselves therefore, and be ye holy; for I am the Lord your God. And ye shall keep my statutes, and do them: I am the Lord which sanctify you.
We are moved by the grace of the Gospel and the work of the Holy Spirit to consecrate ourselves, or to set ourselves apart from self and the world for God’s use. But it is the Lord who does the actual and effective work of sanctifying. He makes us holy in two ways: 1) instantly and officially in Baptism and faith; 2) gradually and actually in the process of growing in faith and love, in which we more and more keep and do.
We don’t actually make ourselves holy, for sinners do not have the ability to improve the flesh and become better people. However, what we do in response to hearing God’s Word of Law and Gospel is set ourselves apart, consecrate, make ourselves available to God, and give Him access. We do this by hearing the Law for conviction of sin that the Spirit might lead us to repentance and the hearing of the Gospel for faith and salvation. The Gospel is the power of God.
We sanctify ourselves by going to church, to Bible study, and to quiet time. Then we respond to the gospel by asking Him to make us better people in the Lord’s Prayer. By using the means of grace we sanctify ourselves so God can make us holy.