John 2:24

24.But Christ did not rely on them. Those who explain the meaning to be, that Christ was on his guard against them, because he knew that they were not upright and faithful, do not appear to me to express sufficiently well the meaning of the Evangelist. Still less do I agree with what Augustine says about recent converts. The Evangelist rather means, in my opinion, that Christ did not reckon them to be genuine disciples, but despised them as volatile and unsteady. It is a passage which ought to be carefully observed, that not all who profess to be Christ’s followers are such in his estimation. But we ought also to add the reason which immediately follows:

Because he knew them all. Nothing is more dangerous than hypocrisy, for this reason among others, that it is an exceedingly common fault. There is scarcely any man who is not pleased with himself; and while we deceive ourselves by empty flatteries, we imagine that God is blind like ourselves. But here we are reminded how widely his judgment differs from ours; for he sees clearly those things which we cannot perceive, because they are concealed by some disguise; and he estimates according to their hidden source, that is, according to the most secret feeling of the heart, those things which dazzle our eyes by false luster. This is what Solomon says, that

God weighs in his balance the hearts of men, while they flatter themselves in their ways, (Proverbs 21:2.)

Let us remember, therefore, that none are the true disciples of Christ but those whom He approves, because in such a matter He alone is competent to decide and to judge.

A question now arises: when the Evangelist says that Christ knew them all, does he mean those only of whom he had lately spoken, or does the expression refer to the whole human race? Some extend it to the universal nature of man, and think that the whole world is here condemned for wicked and perfidious hypocrisy. And, certainly, it is a true statement, that Christ can find in men no reason why he should deign to place them in the number of his followers; but I do not see that this agrees with the context, and therefore I limit it to those who had been formerly mentioned.