This is tricky and delicate primarily because modern theology uses a conspicuous term in a way that is unbiblical but which expresses an idea that is still correct. Let me elaborate. The term is "sanctification" whose use in the Bible is different from that in much of modern theology.
Biblical sanctification is almost always presented as a past completed act so that believers are called "saints", that is, sanctified, meaning "separated to God" (W E Vine) or set apart for a special service to God. 1 Cor 1:30, 2 Thess 2:13, 1 Peter 1:2; and (b) the course of life befitting those so separated, 1 Thess 4:3, 4, 7, Rom 6:19, 22, 1 Tim 2:15, Heb 12:14.
The cognate verb form, hagiazo, to sanctify or set apart, in the New Testament tells us that God’s sanctifying influence on the believer is via His Truth and Word (John 17:17, 19, Acts 20:32) by faith in Jesus (Acts 26:18, 1 Cor 1:2, 2 Tim 2:21, Heb 10:10, 29 ) through the Holy Spirit (Rom 15:16, 1 Cor 6:11). Note that these verbs are past tense, and discuss sanctification as a completed act (see also Heb 13:12).
Theological Sanctification In modern theology, the word “sanctification” is used in a quite different (extra-Biblical) sense of a growing into Christ, Christian development and character building. This is not to suggest that the idea is unbiblical, but rather that the Bible uses different terminology.
Therefore, what modern theology calls "sanctification", the Bible calls various other things such as
- Everyone who has this hope in him purifies himself, just as he is pure. 1 John 3:2, 3. see also 2 cor 7:1
- But you, man of God, flee from all this, and pursue righteousness, godliness, faith, love, endurance and gentleness. Fight the good fight of the faith. Take hold of the eternal life to which you were called when you made your good confession in the presence of many witnesses. 1 Tim 6:11, 12.
- we too may live a new life. Rom 6:4
- offer your bodies as living sacrifices, holy and pleasing to God--this is your spiritual act of worship. Do not conform any longer to the pattern of this world, but be transformed by the renewing of your mind. Then you will be able to test and approve what God's will is – his good, pleasing and perfect will. Rom 12:1, 2
- in all things grow up into him who is the Head, that is, Christ. Eph 4:15, 16
- just as you received Christ Jesus as Lord, continue to live in him, rooted and built up in him, strengthened in the faith as you were taught, and overflowing with thankfulness. Col 2:6, 7.
- you may participate in the divine nature and escape the corruption in the world caused by evil desires. 2 Peter 1:3, 4.
- grow in the grace and knowledge of our Lord and Saviour Jesus Christ. 2 Peter 3:17, 18
Thus, the NT constantly discusses becoming like Christ - a doctrine known as the "Imitation of Christ", 1 John 2:6, . John 13:34, 35, 15:12, 1 John 4:8, 11, 19, Eph 5:1, 2, John 15:13, Eph 5:2, John 16:33, 2 Tim 1:4, Heb 13:12, 13, 1 Peter 2:21, Rom 8:29, Matt 6:12, Eph 4:32, Phil 2:5, 1 Cor 2:16, etc, etc.
In this light, Gal 3:27 and 2 Cor 5:21 are part of this central idea. The Pulpit commentary observes for Gal 3:27
Have put on Christ (Ξριστὸν ἐνεδύσασθε); did put on Christ. In Romans
13:14 we find the imperative used, "Put ye on (ἐνδύσασθε) the Lord
Jesus Christ." There the phrase has an ethical application, denoting
the adoption of that whole system of habits which characterized the
Lord Jesus, and presents in a more definite form that "putting on" of
"the new man" which is insisted upon in Ephesians 4:24. This can
hardly be its meaning here; rather it is to be regarded as a more
determinate form of the notion of" being justified." The penitent
convert, by that decisive action of his faith which by seeking
"baptism into Christ" put forth his hand to lay hold of the
righteousness which is by faith, became invested with this particular
form of "righteousness," namely, that very acceptableness, in the
sight of God, which shone in Christ himself. In that hour God "made
him acceptable in the Beloved" (cf. Ephesians 1:6, ἐχαρίτωσεν ἡμᾶς ἐν
τῷ ἠγαπημένῳ); endued this poor guilty creature with the
loving-kindness with which he regarded his own Son.
Again, Ellicott observes for 2 Cor 5:21
That we might be made the righteousness of God in him.--Better, that
we might become. The "righteousness of God," as in Romans 3:21-22,
expresses not simply the righteousness which He gives, nor that which
He requires, though neither of these meanings is excluded, but rather
that which belongs to Him as His essential attribute. The thought of
St. Paul is that, by our identification with Christ--first ideally and
objectively, as far as God's action is concerned, and then actually
and subjectively, by that act of will which he calls faith--we are
made sharers in the divine righteousness. So, under like conditions,
St. Peter speaks of believers as "made partakers of the divine nature"
(2 Peter 1:4).
Here I want to add some material about the difference between the two texts; more specifically, about the phrase "δικαιοσύνη Θεοῦ" (= righteousness of God, or possibly, justice of God, etc) is a phrase used mostly by Paul but also once by James and once by Peter. Here I will look only at the occurrences by Paul. It occurs in Rom 1:17, 3:5, 21, 22, 10:3, 2 Cor 5:21 - about six times. N T Wright has much to say about this ("What Saint Paul Really Said"). W E Vine observes (Expository Dictionary of NT Words under "Righteousness"):
"Righteousness of God" means essentially the same as His faithfulness,
or truthfulness, that which is consistent with His own nature and
While this absolutely true, it is also equally true we find some important characteristics revealed about this phrase:
- Rom 1:17 - the righteousness of God is revealed in the Gospel and is accepted by faith
- Rom 3:5 - our unrighteousness shows God's Righteousness more clearly (ie by contrast!)
- Rom 3:21, 22 - righteousness of God is revealed apart from the law and it comes [to us] through faith/trust in God
- Rom 10:3 - the Jews did not know the righteousness of God but tried to establish their own
- 2 Cor 5:21 - in him [Christ] we might become the righteousness of God.
What these show is quite significant - while the righteousness of God is an intrinsic part and characteristic of God, it is shared with sinful humans and we are to become the righteousness of God through faith and trust in Him, presumably by the mechanism of 2 Cor 3:18 and Heb 12:2, 3 - "beholding Christ", Fixing our eyes on Him", etc. This is repeated by Peter (2 Peter 1:1-4) who explicitly discusses "partaking of the divine nature". By this, he presumably means what Paul discusses - we take on the attributes and action of God by reflecting Jesus. That is a very similar meaning to Gal 3:27, "putting on Christ".
Note also, 2 Peter 1:1-4 almost links the two concepts of receiving "the righteousness of our God and saviour, Jesus Christ", with "partaking the divine nature".