As Paul seeks to summarize his theological argument for the Galatians in Gal 5:6, he presents a negative and then a positive, what doesn’t matter then what does: “For in Christ Jesus neither circumcision nor uncircumcision matter, but what does matter is faith being energized through love.” The latter phrase is the focus of Paul’s attention, and it is quite powerful in what it affirms. The danger in interpreting it is to assume that Paul speaks generally about faith and love, but that ignores the context of his prior argument in the book. Neither faith nor love are semantically absolute; implied for each is a very particular meaning and content.
The easiest of these to resolve is faith. Faith is never absolute in Galatians; Paul has in mind here faith directed towards Christ Jesus. See Gal 2:16 for a clear, repetitive statement to that effect.
Neither is love absolute, but unclear here is whether this refers to the believer’s love or God’s love. The other occurrences of ἀγάπη in Galatians do not provide clear support for either. This is the first of three times Paul mentions ἀγάπη in the book. The occurrence of the noun in 5:13 is human love between individuals: διὰ τῆς ἀγάπης δουλεύετε ἀλλήλοις, “through love serve each other.” The reference of the other occurrence in 5:22, within the list of the fruit of the Spirit, could refer to either human love or divine love.
The use of the verb ἐνεργέω, “to work, operate,” could help answer the question of which love is in view. The other occurrences of ἐνεργέω in Galatians refer without doubt to God’s work: Gal 2:8 refers to God working equally through Peter and Paul in their respective apostleships, and Gal 3:5 speaks of God working miracles among the Galatians. It is possible, then, that the participle ἐνεργουμένη ultimately refers to God’s activity which energizes faith (the voice of the participle would be passive in this instance). This would mean that ἀγάπη here is God’s love, specifically the love of Christ evidenced in his self sacrifice on the cross (see Gal 2:20), which in turns engenders faith in the individual.
When Paul’s theological arguments are said and done, he can assert a single, important truth: In Christ what matters is faith in him, and that faith is energized through the love of Christ. This last phrase of the verse bears an importance inversely proportional to its brevity. The fundamental structure of the spiritual fabric of the universe has changed. Ethnicity—more specifically, association or non-association with Israel—is of no consequence. Instead, what is effective and has value is a response of faith in Christ, which finds its genesis in the love of God for the individual through the means of Christ’s self-sacrifice on the cross for sin.