Cornelius a Lapide

Even as the testimony of Christ was confirmed in you — i.e., by which, as by two testimonies, the Christian faith was founded and established in you. For the Greeks interpret the Greek k* 0 w, i.e., even as, by enallage, &*>’ through which, that is, the word and knowledge. Others interpret, Even as the testimony , thus : by which things, viz., by the preaching of the Gospel, and by the knowledge of it, as by a sure testimony, it is known that you are faithful and disciples of Christ