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