Who is the one who Sanctify?

We are Sanctified IN God, BY God. Sanctification is not based on human ability to obey.

To the church of God which is at Corinth, to those who are SANCTIFIED IN JESUS CHRIST, called to be saints, with all who in every place call on the name of Jesus Christ our Lord, both theirs and ours:
I Corinthians 1:2 NKJV

that I might be a minister of Jesus Christ to the Gentiles, ministering the gospel of God, that the offering of the Gentiles MIGHT BE ACCEPTABLE, SANCTIFIED BY THE HOLY SPIRIT.
Romans 15:16 NKJV

But of Him you are IN CHRIST JESUS, WHO BECAME FOR US wisdom from God—AND righteousness and SANCTIFICATION and redemption— that, as it is written, “He who glories, let him glory in the Lord .”
I Corinthians 1:30‭-‬31 NKJV

And such were some of you. But YOU WERE WASHED, but YOU WERE SANCTIFIED, but you were justified in the name of the Lord Jesus and by the Spirit of our God.
I Corinthians 6:11 NKJV

Now may the GOD OF PEACE HIMSELF SANCTIFY YOU completely; and may your whole spirit, soul, and body be preserved blameless at the coming of our Lord Jesus Christ.
I Thessalonians 5:23 NKJV

But we are bound to give thanks to God always for you, brethren beloved by the Lord, because God from the beginning CHOSE YOU for salvation through SANCTIFICATION BY THE SPIRIT and belief in the truth,
II Thessalonians 2:13 NKJV

It does not mean Sanctification is effortless. But it does mean that your desire for obedience is given and not achieved.... Rom 15:16 says, "that the offering of the Gentiles might be ACCEPTABLE, SANCTIFIED BY THE HOLY SPIRIT. ". Which means on the flip side, if you think you seek to be justified by your obedience, your Sanctification will not be accepted.