Charles Hodge on Ephesians 4:21

V. 21. If so be ye have heard him. "To hear him does not mean to hear about him. This the apostle in writing to Christians could not express in a hypothetical form. He knew that the Ephesian Christians had heard about Christ. To hear, in this connection, implies intelligence and obedience, as in the frequently occurring phrase, "He that hath ears to hear, let him hear;" and "To-day if ye will hear his voice, &c.," and in a multitude of other cases. To hear the voice of God or of Christ, therefore, is not merely to perceive with the outward ear but to receive with the understanding and the heart. The particle εἴγε, if indeed, does not express doubt; but ‘if, as I take for granted.’ The apostle assumes that they were obedient to the truth. ‘Ye have not so learned Christ as to allow of your living as do the Gentiles, if, as I take for granted, you have really heard his voice and have been taught by him. Ἐν αὐτῷ, however, does not properly mean by him, but ‘in communion with him.’ ‘Ye have been taught in him, inasmuch as truth is in Jesus, to put off the old man.’ The knowledge of Christ, hearing him, union with him, his inward teaching, are necessarily connected with the mortification of sin.

The clause καθώς ἐστιν ἀλήθεια ἐν τῷ Ἰησοῦ, rendered in our version as the truth is in Jesus, is variously explained. The interpretation intimated above supposes καθώς, to have its frequent causal sense; since, inasmuch as; and truth to mean moral truth, or excellence. This sense it very often has. It frequently means true religion, and is used antithetically to unrighteousness, as in Rom. 2, 8. The principle here involved is, that knowledge of God is inconsistent with a life of sin, because knowledge implies love, and God is holy. To know him, therefore, is to love holiness. The apostle’s argument is: ‘If you know Christ you will forsake sin, because he is holy—truth, i. e. moral excellence is in him. If you have been taught any thing in virtue of your communion with him, you have been taught to put off the old man.’

Another interpretation supposes καθώς to mean as, expressing the manner. ‘If ye have been taught as the truth is in Jesus,’ i. e. correctly taught. But this requires the article even in English—the truth, meaning the definite system of truth which Jesus taught. In the Greek, however, the article necessary to give colour to this interpretation is wanting. Besides, the expression "the truth is in Jesus" is obscure and unscriptural, if truth be taken to mean true doctrine. And more than this, this interpretation supposes there may be a true and false teaching by, or in communion with, Christ. This cannot be. The apostle’s hypothesis is, not whether Christ has taught them correctly, but whether he has taught them at all.

A third interpretation makes the following infinitive the subject of the sentence; ‘Truth in Jesus is, to put off the old man.’ The meaning of the whole passage would then be, ‘If you know Christ ye cannot live as the heathen, for truth in Jesus is to put away sin,’ i. e. true fellowship with Christ is to put off, &c. But this violates the natural construction of the passage, according to which the infinitive ἀποθέσθαι depends on ἐδιδάχθητε, ‘Ye have been taught to put off, &c.’ And the expression, ‘It is truth in Jesus to put away sin’ is in itself awkward and obscure. The first mentioned interpretation, therefore, is on the whole to be preferred.