ταύτας οὖν ἔχοντες τὰς ἐπαγγελίας, ἀγαπητοί, καθαρίσωμεν ἑαυτοὺς ἀπὸ παντὸς μολυσμοῦ σαρκὸς καὶ πνεύματος, ἐπιτελοῦντες ἁγιωσύνην ἐν φόβῳ θεοῦ
"Therefore [since] we have these promises, beloved ones, we should purify ourselves from all defilement of the body and spirit, perfecting holiness in the reverence of God"
Beginning with the particle οὖν ("therefore"), Paul indicates that he is not starting a fresh premise. Rather, he is simultaneously summing up what has been said before (i.e. the people of the living God and the Old Testament citation).
Paul's use of the plural form of ἔχοντες designates his focus upon the corporate body of believers, those who have the promises, and specifies that they already have them. The present tense illustrates the current acceptance of these Christians and acknowledges their participation in God's holy calling. The Old Testament citation in the previous chapter deserves to be quoted in full.
“I will live in them and walk among them,
and I will be their God,
and they shall be my people.
Therefore come out from them,
and be separate from them, says the Lord,
and touch nothing unclean;
then I will welcome you,
and I will be your father,
and you shall be my sons and daughters,
says the Lord Almighty.” (NRSV)
It seems this citation is 2 Sam 7:14, although clearly expanded. In any sense, Paul's expansion emphasizes the 'separateness' of God's people as well as the comment on "touch[ing] nothing unclean." The promise worth holding onto is God's dwelling amongst his people, and his calling them "sons and daughter." This is intensified by Paul's use of the noun ἀγαπητοί ("beloved, beloved ones"), suggesting this promise has already been fulfilled and is awaiting perfection, as he will specify later.
Because of this promise, Paul enjoins the believers in Corinth (himself included) to καθαρίσωμεν ("purify") themselves "from all defilement of the body and spirit." Almost all of the uses of the verb καθαρίζω in the New Testament occur in Acts and the Synoptic Gospels, although Paul uses it twice in his other writings. In Eph 5:26, the husband is told to "sanctify" his wife by "cleansing" her (καθαρίζω) with the washing of water. This is probably not a reference to baptism, but rather a symbolic act of submission and of loving tenderness to her, as he is one flesh with her already. Caring for her flesh is caring for himself, and providing a basic requirement of cleanliness is vital for the survival of each other, especially in a time of rampant poverty and disease. The other use in Titus 2:14 is in reference to Christ ransoming himself on behalf of a people, cleansing them from "all lawlessness."
The prepositional phrase ἀπὸ παντὸς μολυσμοῦ σαρκὸς καὶ πνεύματος is fascinating. The word μολυσμοῦ seems to refer to defilement or contamination, and the references to "tainting garments" in Rev 3:4 seems to suggest a stain or a blemish of some sort, although garments are different from people, so this is not an exact or entirely certain parallel image. The point is clear, however: to purify one's self is a free action of the person, empowered by the Holy Spirit, to purify themselves of the blemishes of sin, which seems to already be present in their bodies and their spirits.
Contrary to popular opinion, Paul does not think σαρκὸς ("flesh") is a catchall word referring to the vileness of the human person as if he is a gnostic who detests the body. Rather, the word simply means 'body' apart from the resurrection, at least in this context. Paul's belief in the present nature of the promise of God means that he knows σαρκὸς and the πνεύματος are tainted or stained. The human body, in bondage to sin, is in desperate need of liberation (c.f. Rom 8:23). The believers know this and are ordered to act in response to the promise of God.
The final participial phrase is where the meat is. Paul says ἐπιτελοῦντες ἁγιωσύνην ἐν φόβῳ θεοῦ. The use of the verb ἐπιτελέω is interesting. It is a compound verb (ἐπι + τελέω) that is intensified by the suffix ἐπι. Instead of being merely "to finish" or "to be mature" as τελέω suggests, Paul's use of ἐπιτελέω is like putting an exclamation point after the word and putting it in all caps: PERFECTING (!). The notion of "mature" or "completion" lies at the root of the verb as well.
The fact that ἐπιτελοῦντες is a participial makes this so much more fun. Paul speaks of everyone (himself included) in "perfecting holiness." The noun ἁγιωσύνη ("holiness," "sanctification") occurs 3 times in the New Testament. First in Rom 1:4 where Christ's resurrection is "according to the Spirit of Holiness," and also in 1 Thess 3:13 where believers are enjoined to be "blameless in sanctification before God." Here in 2 Cor 7:1, believers are to be continually active in pursuing and perfecting their sanctification, their set-apartness, as the Old Testament citation states. They live in the "reverence of God," the same God who calls them beloved children.
Sanctification is about completing one's pursuit of God's calling, living a life of tenderness and generosity, seeking purity and gentleness in the hope of God's immanent return. God does not call his people slaves: he calls them his beloved children, children he himself has called. In response to God's call, we submit ourselves and participate in the sanctifying life he has prepared for us. The Holy Spirit, our faithful advocate, and source of empowerment, never ceases in calling God's children into a right relationship with their Father.
Therefore, be constantly perfecting yourself, seeking righteousness, and participating in the promises that await their consummation.
Or, as John Wesley once said:
“By salvation I mean not barely according to the vulgar notion deliverance from hell or going to heaven but a present deliverance from sin a restoration of the soul to its primitive health its original purity a recovery of the divine nature the renewal of our souls after the image of God in righteousness and true holiness in justice mercy and truth.” (Found in An Introduction to World Methodism, p.104).