Christians must eagerly “maintain the unity of the Spirit in the bond of peace,” for Jesus has done everything needed to form a unified body of Jews and Gentiles, establishing one church, pouring out one Spirit, and giving us one hope of resurrection (Eph. 2:11–22; 4:1–4). This is not a superficial unity; it is grounded in one shared body of truth, as today’s passage reveals.
Ephesians 4:5 asserts that there is but “one Lord.” The title Lord, a translation of the Greek term kurios, is one of Paul’s favorite names for Jesus. Since the Septuagint, the Greek translation of the Hebrew Old Testament from which the apostle often quotes, renders the covenant name of God Yahweh as kurios, Paul’s frequent use of the same title for Christ is most interesting. It indicates that he had a high Christology, a doctrine of Christ that equates Him with the one true God and covenant Lord of Israel. Simply put, the apostle viewed Jesus as none other than God Himself. As there is only one Lord, salvation rests in Him alone (John 14:6), and people experience true unity one with another only upon this ultimate foundation.
Besides one Lord, there is also “one faith” (Eph. 4:5), an expression with two possible interpretations: the body of content that is believed (as, for example, in Jude 3) or the subjective experience of faith that all believers have as they trust in Christ alone for redemption. As Matthew Henry writes, the one faith “is the gospel, containing the doctrine of the Christian faith: or, it is the same grace of faith (our trust in Christ) whereby all Christians are saved.” Ultimately, however, these options are not mutually exclusive — in order to find salvation, every person must affirm the same basic body of content and experience the same kind of abandoning trust in everything else but Jesus (Gal. 1:6–9; 2:15–16).
Affirming this same faith and resting on Christ alone, we also share one baptism (Eph. 4:5) — the one baptism of the Spirit by which we are ingrafted into Christ Jesus when we first believe. This invisible baptism is related to water baptism, yet it is not identical to it. Still, just as we are baptized by the Spirit into Christ only one time, so too should we have only one experience of the sacrament that signifies this ingrafting — water baptism into the name of the triune God.