A.T. Robertson Commentary Ephesians 4:21

"if so be that ye heard him, and were taught in him, even as truth is in Jesus:" — Ephesians 4:21 (ASV)

If so be that (ε γε). "If indeed." Condition of first class with aorist indicatives here, assumed to be true (ηκουσατε κα εδιδαχθητε).

Even as truth is in Jesus (καθως εστιν αληθεια εν τω Ιησου). It is not clear what Paul's precise idea is here. The Cerinthian Gnostics did distinguish between the man Jesus and the aeon Christ. Paul here identifies Christ (verse 20) and Jesus (verse 21). At any rate he flatly affirms that there is "truth in Jesus" which is in direct opposition to the heathen manner of life and which is further explained by the epexegetical infinitives that follow (αποθεσθαι, ανανεουσθα δε, κα ενδυσασθα).