Seeing it is one God, which shall justify the circumcision by faith, and uncircumcision through faith.

if so be that God is one, and he shall justify the circumcision by faith, and the uncircumcision through faith.

For it is one God, that justifieth circumcision by faith, and uncircumcision through faith.

since indeed it is one God who shall justify the circumcision on the principle of faith, and uncircumcision by faith.

yes, also of nations; since one is God who shall declare righteous the circumcision by faith, and the uncircumcision through the faith.

unless you can deny that it is one and the same God who will pronounce the circumcised to be acquitted on the ground of faith, and the uncircumcised to be acquitted through the same faith.

If God is one; and he will give righteousness because of faith to those who have circumcision, and through faith to those who have not circumcision.

For One is the God who justifies circumcision by faith and uncircumcision through faith.

Yes, of the Gentiles also, since there is only one God, and he will pronounce those who are circumcised righteous as the result of faith, and also those who are uncircumcised on their showing the same faith.

Quandoquidem unus Deus, qui justificabit circumcisionem ex fide, et Præputium per fidem.

Who shall justify, [1] etc. In saying that some are justified by faith, and some through faith, he seems to have indulged himself in varying his language, while he expresses the same thing, and for this end, -- that he might, by the way, touch on the folly of the Jews, who imagined a difference between themselves and the Gentiles, though on the subject of justification there was no difference whatever; for since men became partakers of this grace by faith only, and since faith in all is the same, it is absurd to make a distinction in what is so much alike. I am hence led to think that there is something ironical in the words, as though be said, -- "If any wishes to have a difference made between the Gentile and the Jew, let him take this, -- that the one obtains righteousness by faith, and the other through faith." But it may be, that some will prefer this distinction, -- that the Jews were justified by faith, because they were born the heirs of grace, as the right of adoption was transmitted to them from the Fathers, -- and that the Gentiles were justified through faith, because the covenant to them was adventitious.

Footnotes

1 - The future is used for the present -- "who justifies," after the manner of the Hebrew language, though some consider that the day of judgment is referred to; but he seems to speak of a present act, or as Grotius says, of a continued act, which the Hebrews expressed by the future tense. -- Ed.

Seeing it is one God - επιπερ εις ο θεος. This has been rendered, Seeing God is one. It however makes little difference in the sense: the apostle's meaning most evidently is, it is one and the same God who made both Jews and Gentiles, who shall justify - pardon, the circumcision - the believing Jews, by faith; and the uncircumcision - the believing Gentiles, by the same faith; as there is but one Savior and one atonement provided for the whole.
It is fanciful to suppose that the apostle has one meaning when he says, εκ πιστεως, By faith, and a different meaning when he says, δια της πιστεως, Through faith. Both the prepositions are to be understood in precisely the same sense; only the addition of the article της, in the last case, extends and more pointedly ascertains the meaning. It is one and the same God who shall justify the believing Jews by faith; and the believing Gentiles δια της πιστεως, by That Same faith.

Seeing [it is] one God, which shall justify (g) the circumcision by faith, and uncircumcision through faith.
(g) The circumcised.

Seeing it is one God,.... God is one in nature and essence, though there are three persons in the Godhead, Father, Son, and Holy Ghost; whence it appears, that he that is the God of the Jews, is also the God of the Gentiles, or there would be more gods than one; and that these are justified in one and the same manner, or God must be divided; for God, as he is one in nature, so he is one in will, in his promises, and in the methods of his grace:
which shall justify the circumcision by faith, and uncircumcision through faith. The objects of justification are "the circumcision", the circumcised Jews, and "the uncircumcision", the uncircumcised Gentiles; the circumcision of the one does not forward, and the uncircumcision of the other does not hinder, nor neither of them effect the grace of justification: the justifier of them is one and the same, who is God; and the matter of their justification is the same, which is the righteousness of Christ; and the manner of it, or the means of their comfortable apprehension of it, is the same; for those phrases, "by faith", and "through faith", mean one and the same thing; see Philippians 3:9.

it is one God who shall justify--"has unchangeably fixed that He shall justify."
the circumcision by--"of"
faith, and the uncircumcision through faith--probably this is but a varied statement of the same truth for greater emphasis (see Romans 3:22); though BENGEL thinks that the justification of the Jews, as the born heirs of the promise, may be here purposely said to be "of faith," while that of the Gentiles, previously "strangers to the covenants of promise," may be said to be "through faith," as thus admitted into a new family.
Objection:

Seeing it is one God who - Shows mercy to both, and by the very same means.