Ephesians emphasizes the need “to equip the holy ones for the work of ministry, for building up the body of Messiah, until we attain to the unity of the faith” (Eph 4:12-13). In trying to understand “the unity of the faith,” a difficulty arises in the fact that, outside of Ephesians 4, the term for “unity” (ἑνότης; enótes) appears nowhere in the New Testament. Since words only have meaning in context, the scarcity of ἑνότης doesn’t give the interpreter much to go on. However, the idea of unity among a faith community has precedent in the Dead Sea Scrolls, which describe the Qumran sect as a tight-knit “unity” based on communal rules that encourage righteous behavior. Similarly, Ephesians uses “unity of the faith” to signify a cohesive assembly of Jesus-followers whose behavior is founded on a set of beliefs that promote holiness.
The outset of Ephesians 4 encourages “bearing one another in love, eager to maintain the unity (ἑνότης; enótes) of the Spirit in the bond of peace” (4:2-3). Since this reference to “the unity of the Spirit” precedes the reference to “the unity of the faith” (4:13), there seems to be a relationship between the “Spirit” and “faith.” A specific set of realities, all of which are marked by oneness, lead to the state of unity: “One body and one Spirit (ἓν πνεῦμα; èn pneuma)… one Lord, one faith (μία πίστις; mía pístis), one baptism, one God and Father of all” (4:4-6). The one Spirit binds the one body of Christ, which is a community of that adheres to the “one faith” in one Lord (Jesus) and one God (the Father). The affirmation of “the faith” leads to behavior that reflects the love of Jesus, whose death was a “fragrant offering and sacrifice to God” (5:2). To this end, believers are to avoid sexual immorality, impurity, foolish talk, covetousness, idolatry (5:3-21)—expelling these negative acts from the body of Christ allows the congregation to be “filled with the Spirit” (5:18).
An idea similar to “the unity of faith” appears at Qumran; the Dead Sea Scrolls call its community of believers the “Yahad” (יחד), or “Unity.” A text known as the Community Rule lays out specific communal legislation for members so that “they may abstain from all evil and hold fast to all good” (1QS 1:4), and thus “lay a foundation of truth for Israel, for the Yahad… a most holy dwelling (literally, “holy of holies” [קודשׁ קודשׁים; qodesh qodeshim]) for Aaron and house of perfection and truth in Israel” (5:5; 8:8-10). As “children of light,” the members of the Yahad “walk in the ways of light” and become a dwelling place for God (3:20-24). Ephesians uses these same words of those who attain “unity” in Messiah: “Now you are light in the Lord. Walk as children of light, for the fruit of light is found in all good and righteousness and truth” (Eph 5:8-9). More, believers in Yeshua are “built on the foundation of the apostles and prophets” as a “holy temple in the Lord… a dwelling for God in the Spirit” (2:20-21). These similarities show that Ephesians envisions a messianic Yahad whose behavior reflects the “unity of the faith” in Jesus the Messiah.