John 14:21

21.He who hath my commandments. He again repeats the former statement, that the undoubted proof of our love to him lies in our keeping his commandments; and the reason why he so frequently reminds the disciples of this is, that they may not turn aside from this object; for there is nothing to which we are more prone than to slide into a carnal affection, so as to love something else than Christ under the name of Christ. Such is also the import of that saying of Paul,

Though we have known Christ after the flesh, yet henceforth we know him no longer in this manner. Let us therefore be a new creature,
(2 Corinthians 5:16.)

To have his commandments means to be properly instructed in them; and to keep his commandments is to conform ourselves and our life to their rule.

And he that loveth me will be loved by my Father. Christ speaks as if men loved God before he loved them; which is absurd, for,

when we were enemies, he reconciled us to him,
(Romans 5:10;)

and the words of John are well known,

Not that we first loved him, but he first loved us,
(1 John 4:10.)

But there is no debate here about cause or effect; and therefore there is no ground for the inference, that the love with which we love Christ comes in order before the love which God has toward us; for Christ meant only, that all who love him will be happy, because they will also be loved by him and by the Father; not that God then begins to love them, but because they have a testimony of his love to them, as a Father, engraven on their hearts. To the same purpose is the clause which immediately follows: —

And I will manifest myself to him. Knowledge undoubtedly goes before love; but Christ’s meaning was, I will grant to those who purely observe my doctrine, that they shall make progress from day to day in faith; “that is, “I will cause them to approach more nearly and more familiarly to me. ” Hence infer, that the fruit of piety is progress in the knowledge of Christ; for he who promises that he will give himself to him who has it rejects hypocrites, and causes all to make progress in faith who, cordially embracing the doctrine of the Gospel, bring themselves entirely into obedience to it. And this is the reason why many fall back, and why we scarcely see one in ten proceed in the right course; for the greater part do not deserve that he should manifest himself to them It ought also to be observed, that a more abundant knowledge of Christ is here represented as an extraordinary reward of our love to Christ; and hence it follows that it is an invaluable treasure.