For what the Law could not do (this is certainly what is meant by τὸ ἀδύνατον τοῦ νόμου), in that it was weak through the flesh, God sending his own Son in likeness of flesh of sin, and for sin, condemned sin in the flesh.
The Law could not deliver from the domination of sin; it was weak for such a purpose (cf. Hebrews 7:18, Hebrews 7:19) but this not through any defect in itself but as having to work through our sinful flesh which refused obedience.
And it was not the office of law to regenerate; it could only command and threaten. Hence the deliverance came, and could only come, from God himself (and this in accordance with the grand idea of the whole Epistle, expressed by the phrase, "the righteousness of God"); and so he sent his own Son (i.
e. his Son essentially—in a sense in which none of us can be called sons, himself Divine. The whole drift of the passage, as well as ἑαυτοῦ, requires this conception); and he sent him into the very sphere of things that required redemption, that by actual participation in it he might personally redeem it; for he sent him in likeness of our "flesh of sin."
It is not said in flesh of sin; for that might imply sin in Christ's individual humanity: but, on the other hand, "in likeness" ( ἐν ὁμοιώματι) does not imply docetism, as though Christ's humanity were not real; for stress is evidently laid on the fact that it was in our actual human flesh that he "condemned" sin.
The phrase appears to mean the same as what is expressed in Hebrews 2:17 and Hebrews 4:15 : ὤφειλε κατὰ πάντα τοῖς ἀδελφοῖς ὁμοιωθῆναι, and πεπειραμένον κατὰ πὰντα κααθ ὁμοιότητα χαρὶς ἁμαρτίας.
The addition of περὶ ἀμαρτίας "adds to the how the wherefore" (Meyer). Both this and the preceding expression are most naturally and intelligibly connected with τέμψας; not, as some say, with κατέκρινε.
περὶ comes suitably after the former verb, as denoting the occasion and purpose of the sending (cf. προσένεγκε περὶ τοῦ καθαρισμοῦ, Luke 5:14). In Hebrews 10:8 (quoting from Psalms 40:7 in the LXX.
) we find θυσίαν καὶ προσφορὰν καὶ ὁλοκαυτώματα καὶ περὶ ἁμαρτίας, where the expression signifies offerings for sin; and in Hebrews 10:18 we have προσφορὰ περὶ ἁμαρτίας. The correspondence of phrase here suggests decidedly the idea of the purpose of atonement being intended to be expressed by it, though it does not follow that περὶ ἁμαρτίας is used here substantively as it seems to be in Hebrews 10:8.
But in what sense are we to understand condemned ( κατέκρινε) sin? We observe first that the verb appears to be suggested by κατάκριμα in Hebrews 10:1, the connection being that formerly sin condemned us, but now sin itself has been condemned; that is (as Meyer expresses it), deposed from its rule in the flesh—"jure sue dejectum" (Calvin).
(Perhaps similarly, John 16:11, ὁ ἄρχων τοῦ κόσμου τούτου κέκριται.) One view of the force of κατέκρινε (found in Origen, and taken by Erasmus and others), that it denotes the punishment of sin endured by Christ vicariously on the cross, is not only not obvious, but inconsistent also with τὸ ἀδύνετον τοῦ νόμου preceding; for what the Law could not do, was not to punish sin, but to deliver from it.
Nor is there, further, anything in the language used to confine the condemnation of sin, in whatever sense intended, to the atonement made for it on the cross itself. It was in the whole mission of the Saviour (expressed by πέμψας) that sin was "condemned;" and the idea may include his triumph over it in his human life no less than the penalty paid for it on the cross in behalf of man.
"In the flesh" (connected with condemned, not with sin) does not mean Christ's own flesh, but human nature generally. He represented man, having become for our sake the Soul of man; and we share his triumph over sin, made in our very human flesh, when we are baptized into his death, and become thereupon partakers of his resurrection.
This idea, ever present to St. Paul's mind, is expressed in the next verse, where our own appropriation of the condemnation of sin in Christ is declared.