1 John 2:4

For true faith is that which does not contradict in conduct what it says in words. Hence it is that Paul says of certain false believers: "They profess to know God, but they deny Him by their deeds." Hence John says: "He who says he knows God and does not keep His commandments is a liar." Since this is so, we ought to recognize the truth of our faith in the consideration of our life. For then we are truly faithful, if we fulfill in works what we promise in words. On the day of baptism indeed, we promised to renounce all the works of the ancient enemy and all his pomps. Therefore let each of you bring back the eyes of his mind to consideration of himself; and if he keeps after baptism what he pledged before baptism, let him rejoice, now certain that he is faithful. But behold, if he has by no means kept what he promised, if he has slipped into practicing wicked works, into desiring the pomps of the world; let us see if he now knows how to lament that he has erred. For before the merciful Judge, not even he will be held a deceiver who returns to the truth, even after he has lied, because almighty God, when He willingly receives our repentance, Himself hides by His own judgment that in which we have erred.

It is obvious that the person who does not keep God's commandments has no knowledge of him.

Whoever says he knows Him but does not keep His commandments, etc. Christ is called the truth: "I am" (He says) "the way, the truth, and the life" (John XIV). Therefore, it is futile for us to boast about knowing Him when we do not …

And from the contrary he confirms the same thing, employing the most complete proof.

And, if that be seen and known, how vain and superficial is even this knowledge when it sways not the heart unto obedience! A disobedient life is the confutation and shame of pretended religious knowledge; it gives the lie to such boasts and pretences, and shows that there is neither religion nor honesty in them.

He that saith I know him,....

He that saith, I know him - This is a severe blow against those false teachers, and against all pretenders to religious knowledge, who live under the power of their sins; and against all Antinomians, and false boasters in the righteousness of Christ as a covering for their personal unholiness. They are all liars, and no truth of God is in them.

THE Epistles of John possess and combine certain qualities which seem, at the first blush, to stand opposite as the poles to one another. Their style of expression is simple, chaste, and unadorned. Short words are used. For the most part words of one syllable—such little homely words as a young child might easily spell. And the sense is so clear and obvious, that the captious critic or the astute reasoner must be puzzled to distort it. Yet there is no lack of dignity in the language, and as for the matter of these Epistles, it is grand and sublime. Where would you turn in the pages of the New Testament, save only to the book of the Revelation, given by the pen of the same writer, for more notable mystery? The language charms our ears, while the Truth it expresses holds us in awe. There are deep meanings and veiled mysteries here. Albeit the hidden wisdom which baffles finite thought is not couched in strange terms, but declared in such plain speech as trips lightly off the tongue, and yet sinks deeply into the heart. Again, the spirit of John is love, all love. Every line he writes is perfumed with charity. And yet to what close self-examination, to what a severe testing does he put us! How truly may it be said that these Epistles are a touchstone by which we may discern between the true gold and the counterfeit! Generous but discriminating, glowing with affection but rigid in fidelity, the Apostle mingles caution with caress, and qualifies the most soothing consolations with such stern warnings, that in well-near every sentence he constrains us to deep searching of heart. The text is a case in point. With a wise discrimination he draws a contrast between him who knows that he knows Christ, and him who says that he knows Christ.

THE Epistles of John possess and combine certain qualities which seem, at the first blush, to stand opposite as the poles to one another. Their style of expression is simple, chaste, and unadorned. Short words are used. For the most part words of one syllable—such little homely words as a young child might easily spell. And the sense is so clear and obvious, that the captious critic or the astute reasoner must be puzzled to distort it. Yet there is no lack of dignity in the language, and as for the matter of these Epistles, it is grand and sublime.

He that saith, I know Him - He who professes to be acquainted with the Saviour, or who professes to be a Christian. And keepeth not his commandments - What he has appointed to be observed by his people; that is, he who does not obey him. Is a liar - Makes a false profession; professes to have that which he really has not. Such a profession is a falsehood, because there can be no true religion where one does not obey the law of God.