Ephesians 4:5

The one Lord is Jesus Christ, the Head of the church (Ephesians 1:22-23; Colossians 1:18). The one faith is probably the faith that each Christian and the whole church have in Christ rather than Christianity viewed as a faith (cf. Colossians 2:7). This identification unites faith with Christ in the context (Ephesians 2:8).

The one baptism may be the baptism that unites all believers in the body of Christ. This is Spirit baptism, which water baptism symbolizes. Both kinds of baptism were probably in Paul’s mind. [Note: Morris, p. 119.] However baptism falls in the second triad of elements that relate to Christ rather than to the first that relate to the Spirit in this verse. Therefore it probably refers to water rather than to Spirit baptism. Another possibility is that it refers metaphorically to the believer’s baptism into Christ’s death. In this case the "one baptism" would refer to the internal reality of having been baptized into (identified with) the "one Lord" by means of the "one faith." [Note: Hoehner, Ephesians, p. 518.]