“As the truth is in Jesus;” it is not doctrine, though doctrine is contained in it. The truth as it is in Jesus is the having put off the old man and put on the new —this having been done by faith. Then he adds, “and being renewed in the spirit of your mind.” The putting off and the putting on are not in the present tense, whereas being renewed in the spirit of your mind is. The truth is, that you have put off the old man, but you do want renewing. In Colossians (chap. 3) it is distinct: “Lie not one to another, seeing ye have put off the old man with his deeds and have put on the new.”
In the epistle to the Ephesians he is not saying directly to them what they have done, but saying what the truth is in Jesus. So it is more abstract. The truth in Jesus is having put off and having put on. Being renewed is present — the renewing of the spirit of your mind is a thing that is always going on.
J. N. Darby