While the Bible is full of exhortations and encouragement on how Christians are to be sanctified, the character of believers has been supernaturally changed by the power of God in a way that causes them to pursue holiness and sanctification. It is not that they should BE SANCTIFIED it is THEY ARE SANCTIFIED! Irresistible grace does not end with justification. Christians are not saved by grace and sanctified by human effort. We are saved by irresistible grace and sanctified by irresistible grace. Since sanctification is assured [John 17:17 Sanctify them in the truth; your word is truth.], it is dangerously close to a faith plus works salvation to assert that human effort is needed for sanctification apart from grace. Paul explained this well in the following passage: “1 Cor. 15:10 But by the grace of God I am what I am, and his grace toward me was not in vain. On the contrary, I worked harder than any of them, though it was not I, but the grace of God that is with me.” Here Paul gives 100% of the credit to the grace of God.
The Old Covenant has been made obsolete by the new and better New Covenant. New Covenant believers are given new hearts by divine power and sanctified by divine power. The following passage describes a God caused sanctification:
Hebrews 8:10-11 For this is the covenant that I will make with the house of Israel after those days, declares the Lord: I will put my laws into their minds, and write them on their hearts, and I will be their God, and they shall be my people. And they shall not teach, each one his neighbor and each one his brother, saying, ‘Know the Lord,’ for they shall all know me, from the least of them to the greatest.
While believers freely come to Jesus Christ and freely respond in sanctification, it is caused by divine intervention [grace].