I just read an excellent chapter in Wayne Grudem’s Systematic Theology on what it means to be filled with the Holy Spirit, and how to rightly understand the experience that Pentecostals call a “baptism in the Spirit.” This particular section was so good, that I’m going to quote it at length.
“We see examples of repeated filling with the Holy Spirit in the book of Acts. In Acts 2:4, the disciples and those with them were “all filled with the Holy Spirit.” Later, when Peter was standing before the Sanhedrin, we read, “Then Peter, filled with the Holy Spirit, said to them…” (Acts 4:8). But a little later, when Peter and the other apostles had returned to the church to tell what had happened (Acts 4:23) they joined together in prayer. After they had prayed there were again filled with the Holy Spirit, a sequence of events that Luke makes clear: “After they prayed, the place where they were meeting was shaken. And they were all filled with the Holy Spirit and spoke the Word of God boldly” (Acts 4:31). Even though Peter had been filled with the Holy Spirit at Pentecost (Acts 2:4) and had later been filled with the Holy Spirit before speaking to the Sanhedrin (Acts 4:8), he was once again filled with the Holy Spirit after the group of Christians he was meeting with had prayed.
Therefore, it is appropriate to understand filling with the Holy Spirit not as a one-time event but as an event that can occur over and over again in a Christian’s life. It may involve a momentary empowering for a specific ministry (such as apparently happened in Acts 4:8; 7:55), but it may also refer to a long-term characteristic of a person’s life (see Acts 6:3; 11:24)…
Someone might object that a person who is already “full” of the Holy Spirit cannot become more full – if a glass if full of water no more water can be put into it. But a water glass is a poor analogy for us as real people, for God is able to cause us to grow and to be able to contain much more of the Holy Spirit’s fullness and power. A better analogy might be a balloon, which can be “full” of air even though it has very little air in it. When more air is blown in, the balloon expands and in a sense it is “more full.” So it is with us: we can be filled with the Holy Spirit and at the same time be able to receive much more of the Holy Spirit as well. It was only Jesus himself to whom the Father gave the Spirit without measure (John 3:34).
The divisiveness that comes with the term “baptism in the Holy Spirit” could easily be avoided by using any of the alternative terms mentioned in this section. People could be thankful for “a new fullness of the Holy Spirit” or “a new empowering for ministry” or “a significant step in growth” in some aspect of another Christian’s life. ”
-Grudem, Systematic Theology, p. 782