Christopher Love unpacks the clause of Romans 8:13, “But if ye by the Spirit do mortify …” and demonstrates the manner in which the Spirit is the agent of sanctification. First, the Spirit is called the Holy Spirit, for his “proper office is to make a man holy” (89).
Second, sanctification is attributed to the Spirit:
1 Peter, an apostle of Jesus Christ, To those who are elect exiles of the Dispersion in Pontus, Galatia, Cappadocia, Asia, and Bithynia, 2 according to the foreknowledge of God the Father, in the sanctification of the Spirit, for obedience to Jesus Christ and for sprinkling with his blood: May grace and peace be multiplied to you. 1 Peter 1:1–2 (ESV)
And such were some of you. But you were washed, you were sanctified, you were justified in the name of the Lord Jesus Christ and by the Spirit of our God. 1 Corinthians 6:11 (ESV)
Sanctification consists of both vivification, being alive toward God; and mortification, being dead toward sin. Therefore, the Spirit must be the agent of mortification.
Third, the Lord states that the Spirit is sent to bring conviction of sin:
And when he comes, he will convict the world concerning sin and righteousness and judgment: John 16:8 (ESV)
Conviction of sin brings turning from sin:
A man will never seek after a cure until he is sensible of his disease. So you will never go about the extirpation of sin until you are sensible of the danger and guilt of your sins. You will never be convinced of the danger and evil of sin unless the Spirit of God enlightens you. The work of mortification is wholly ascribed to the Spirit of God because only He can convince us of the Evil of Sin so as to make us hate and abhor it and strive against it.