These things I have spoken to you. He adds, that his love is far from being unknown to the godly, but that it is perceived by faith, so that they enjoy blessed peace of conscience; for the joy which he mentions springs from that peace with God which is possessed by all that have been justified by free grace. As often, then, as God's fatherly love towards us is preached, let us know that there is given to us ground for true joy, that, with peaceable consciences, we may be certain of our salvation. My joy and your joy. It is called Christ's joy and our joy in various respects. It is Christ's, because it is given to us by him; for he is both the Author and the Cause of it. I say that he is the Cause of it, because we were freed from guilt, when the chastisement of our peace was laid on him, (Isaiah 53:5.) I call him also the Author of it, because by his Spirit he drives away dread and anxiety in our hearts, and then arises that calm cheerfulness. It is said to be ours for a different reason; because we enjoy it since it has been given to us. Now since Christ declares that he spake these things, that the disciples might have joy, we conclude from these words, that all who have duly profited by this sermon have something on which they can rest. That my joy may abide in you. By the word abide he means, that it is not a fleeting or temporary joy of which he speaks, but a joy which never fails or passes away. Let us therefore learn that we ought to seek in the doctrine of Christ the assurance of salvation, which retains its vigor both in life and in death. That your joy may be full. He adds, that this joy will be solid and full; not that believers will be entirely free from all sadness, but that the ground for joy will be far greater, so that no dread, no anxiety, no grief, will swallow them up; for those to whom it has been given to glory in Christ will not be prevented, either by life, or by death, or by any distresses, from bidding defiance to sadness.

These things - The discourse in this and the previous chapter. This discourse was designed to comfort them by the promise of the Holy Spirit and of eternal life, and to direct them in the discharge of their duty.
My joy - This expression probably denotes the happiness which Jesus had, and would continue to have, by their obedience, love, and fidelity. Their obedience was to him a source of joy. It was that which he sought and for which he had labored. He now clearly taught them the path of duty, and encouraged them to persevere, notwithstanding he was about to leave them. If they obeyed him, it would continue to him to be a source of joy. Christ rejoices in the obedience of all his friends; and, though his happiness is not dependent on them, yet their fidelity is an object which he desires and in which he finds delight. The same sentiment is expressed in John 17:13.
Your joy might be full - That you might be delivered from your despondency and grief at my departure; that you might see the reason why I leave you, be comforted by the Holy Spirit, and be sustained in the arduous trials of your ministry. See 1-John 1:4; 2-John 1:12. This promise of the Saviour was abundantly fulfilled. The apostles with great frequency speak of the fulness of their joy - joy produced in just the manner promised by the Saviour - by the presence of the Holy Spirit. And it showed his great love, that he promised such joy; his infinite knowledge, that, in the midst of their many trials and persecutions, he knew that they would possess it; and the glorious power and loveliness of his gospel, that it could impart such joy amid so many tribulations. See instances of this joy in Acts 13:52; Romans 14:17; 2-Corinthians 2:3; Galatians 5:22; 1-Thessalonians 1:6; 1-Thessalonians 2:19-20; 1-Thessalonians 3:9; 1-Peter 1:8; Romans 5:11; 2-Corinthians 7:4.

That my joy may remain in you - That the joy which I now feel, on account of your steady, affectionate attachment to me, may be lasting, I give you both warnings and directions, that ye may abide in the faith.
That your joy might be full - Or, complete - πληρωθη, filled up: a metaphor taken from a vessel, into which water or any other thing is poured, till it is full to the brim. The religion of Christ expels all misery from the hearts of those who receive it in its fullness. It was to drive wretchedness out of the world that Jesus came into it.
Bishop Pearce, by joining εν εμοι to χαρα, and not to μεινῃ, translates the verse thus: These things have I spoken, that my joy in you may remain - which is according to the meaning given to the first clause.

These things have I spoken unto you,.... Concerning the vine and branches, his abiding in them, and they in him, their fruitfulness from him, and perseverance in him, his love to them, and theirs to him:
that my joy might remain in you; meaning either that joy with which he joyed in and over them, as united to him, and which is of the same nature as the joy of the bridegroom over the bride, and which will always remain and continue the same; or rather that joy which he is the author, object, ground, and matter of, for there is always reason to rejoice in him, even in the most afflictive circumstances of life:
and that your joy might be full; that grace of joy which is implanted in the soul, by the Spirit of God in regeneration, and arises from, and is increased by discoveries of the person, grace, blood, righteousness, and sacrifice of Christ; and is "full of glory", 1-Peter 1:8; upon a clear sight of him in this life, and will be entirely full, completely perfected in the other world, when he will be seen as he is,

These things have I spoken . . . that my joy may remain in you. Strange words, that one about to be crucified should speak of his joy! His joy was union with and presence of the Father. He had "anointed him with the oil of gladness above his fellows." He desired his disciples to have that joy, the constant consolation of the sense of the presence of Christ.

That my joy might remain in you - The same joy which I feel in loving the Father, and keeping his commandments.