The final thing we learn from Jesus about the Spirit in John 14:16-18 is this: though the world cannot accept the Spirit of truth, we who are believers in Jesus know the Spirit, for the Spirit lives with us and will be in us. Jesus says, "I will not leave you as orphans; I will come to you."
Jesus promised his first disciples that he would not leave them alone on the earth to carry out his mission after his death and resurrection. He promised to send the Holy Spirit to help them. Indeed, Jesus did just that on Pentecost, approximately fifty days after uttering these words in John 14.
Jesus tells us that the one who comes alongside of us (the paraclete) is also the one who will be in us. I do not think Jesus was promising a fundamental change in the location of the Spirit in relation to his disciples, a movement from alongside to inside. I say this because the "alongside" relationship of the Holy Spirit not only took place during Jesus' earthly ministry but also later, after Jesus left his disciples physically. We see this in verses 23, 25 and 26 of John 14. Furthermore, some of the early manuscripts of John 14 have Jesus saying, "But you know him, for he lives with you and is in you."
Certainly, the Holy Spirit lived in believers before Pentecost. How else could the disciples have performed the miracles they carried out? Even in the Old Testament, why would David have prayed to the Lord, "Take not your Holy Spirit from me" if the Holy Spirit was not living in him? How could Old Testament saints like Abraham have had faith without the help of the Holy Spirit? It seems obvious to me that the Holy Spirit was alive and active in believers before Pentecost. What was new at Pentecost was that the Holy Spirit was poured out for the first time on Jesus' newly constituted, new covenant church. At Pentecost, for the first time, the flood light of the Holy Spirit was being turned on the completed work of Christ to fully reveal all that he had said and done.
Of course, what is more crucial for us to understand is not when the Holy Spirit first came to live in believers in the past, but the fact that the Holy Spirit can live in us now. Paul says, "Having believed, you were marked in him with a seal, the promised Holy Spirit." (Ephesians 1:13) When we believe in Jesus, when we trust in him to save us from our sin, the Holy Spirit not only comes alongside of us, but is in us. What great news! We are not orphans; we are sons and daughters of the living God when we believe in his Son. And the Holy Spirit living in us will give us assurance of our relationship with God and enable us to call God "Abba" (Daddy) just as Jesus did. The Holy Spirit can live right now in anyone who accepts him; the Spirit can give us an intimate relationship with God and quench our spiritual thirst; the Spirit can put the music of the ages into our lives.
The story is told of a fisherman who was weathering a terrible storm in a tiny boat. He prayed in the midst of the storm, "Lord, I am in trouble, and I need your help. Please come yourself. This ain't no time for boys." When we go through storms in life we can call out to the Lord just as that fisherman did and we can count on the fact that the Lord will be present for us through his Holy Spirit.
Ephesians 5:18 says, "Be filled with the Spirit." We as believers in Jesus already have the Spirit in our lives. But what we as believers also need on a daily basis is to be filled with the Spirit, to come under the Spirit's full control and influence, to surrender to the Spirit's divine, personal, encouraging, truthful, indwelling ministry in our lives. If we ask God to "fill the sails" of our lives with the wind of his Spirit, he will do that. After all, Jesus promised, "If you then, though you are evil, know how to give good gifts to your children, how much more will your Father in heaven give the Holy Spirit to those who ask him!"
This does not mean that we will always feel the presence of the Spirit in our lives. However, whenever we ask for more of the Spirit, God will give his Spirit to us, whether we feel him or not.
I love what C. S. Lewis once said about this in a letter to Mary Willis Shelburne....
The act wh. engenders a child ought to be, and usually is, attended by pleasure. But it is not the pleasure that produces the child. Where there is pleasure there may be sterility: where there is no pleasure the act may be fertile. And in the spiritual marriage of God & the soul it is the same. It is the actual presence, not the sensation of the presence, of the Holy Ghost wh. begets Christ in us. The sense of the presence is a super-added gift for wh. we give thanks when it comes, and that's all about it. (February 20, 1955)