A.T. Robertson Commentary Ephesians 3:4

"whereby, when ye read, ye can perceive my understanding in the mystery of Christ;" — Ephesians 3:4 (ASV)

Whereby (προς ο). "Looking to which," "according to which."

When ye read (αναγινωσκοντες). This Epistle will be read in public.

My understanding in the mystery of Christ (την συνεσιν μου εν τω μυστηριω του Χριστου). My "comprehension" (συνεσιν, Colossians 1:9; 2:2). Every sermon reveals the preacher's grasp of "the mystery of Christ." If he has no insight into Christ, he has no call to preach.