Jamieson, Fausset & Brown

one spirit--with Him. In the case of union with a harlot, the fornicator becomes one "body" with her (not one "spirit," for the spirit which is normally the organ of the Holy Spirit in man, is in the carnal so overlaid with what is sensual that it is ignored altogether). But the believer not only has his body sanctified by union with Christ's body, but also becomes "one spirit" with Him (Joh 15:1-7; Joh 17:21; Pe2 1:4; compare Eph 5:23-32; Joh 3:6).