Jamieson, Fausset and Brown on Ephesians 4:5

5. Similarly "faith" and "baptism" (the sacramental seal of faith) are connected (Mr 16:16; Col 2:12). Compare 1Co 12:13, "Faith" is not here that which we believe, but the act of believing, the mean by which we apprehend the "one Lord." "Baptism" is specified, being the sacrament whereby we are incorporated into the "one body." Not the Lord's Supper, which is an act of matured communion on the part of those already incorporate, "a symbol of union, not of unity" [Ellicott]. In 1Co 10:17, where a breach of union was in question, it forms the rallying point [Alford]. There is not added, "One pope, one council, one form of government" [Cautions for Times]. The Church is one in unity of faith (Ep 4:5; Jude 3); unity of origination (Ep 2:19-21): unity of sacraments (Ep 4:5; 1Co 10:17; 12:13): unity of "hope" (Ep 4:4; Tit 1:2); unity of charity (Ep 4:3): unity (not uniformity) of discipline and government: for where there is no order, no ministry with Christ as the Head, there is no Church [Pearson, Exposition of the Creed, Article IX].