Remain in me, and I will remain in you. Just as the branch cannot bear fruit by itself, unless it remains in the vine, so neither can you unless you remain in me.
[John 15:4 NET]
The Lord did not use these words as though there were any power in the creature to abide in him. But he was pleased to use them, that they might be blessed to his people when the Holy Spirit applied them to the heart; for he adds, “And I in you.” The one is the key to the other. If we abide in Christ, Christ abides in us. It is by Christ abiding in us, that we are enabled to abide in him.
But how does Christ abide in us? By his Spirit. It is by his Spirit he makes the bodies of his saints, his temple; it is by his Spirit that he comes and dwells in them. Though it is instrumentally by faith, as we read, “that Christ may dwell in your hearts by faith;” yet it is through the communication of his Spirit in the soul, and the visits of his most gracious presence. Thus he bids us, encourages us, and influences us to abide in him by his abiding in us.
But his abiding in a child of God may be known by certain effects following. If he abides in you, he makes and keeps your conscience tender. It is sin that separates between you and him. Therefore, the Lord Jesus Christ, in order that he may abide in you and make you abide in him, makes and keeps your conscience tender in his fear. And this keeps you from those sins which separate between you and him. He may be known, then, to abide in you by the secret checks he gives you when temptation comes before your eyes, and you are all but gone; as one of old said, “My feet were almost gone; my steps had well-near slipped.” He is pleased to give a secret internal check and admonition; so that your cry is, “How can I do this great wickedness and sin against God?”
And if you go astray and turn from the Lord to your idols, as to our shame and sorrow we often do, he proves that he still abides in you by not giving you up to a reprobate mind, not allowing you to harden your heart against him; but by his reproofs, admonitions, and secret checks in your conscience—by the very lashings and scourgings which he inflicts upon you as a father upon his child, and his secret pleadings with you in the court of conscience—by all these things he makes it manifest that he still abides in you.