What is the "filling of the Spirit"?

In two places in the Acts 4:1-31, Luke tells us that people were "filled with the Holy Spirit." The first reference is v. 8, where Peter begins to answer the Sanhedrin regarding the healing he and John had performed the previous day. The second reference is in verse 31, where all the praying church were filled with the Spirit. But Luke doesn't go into much detail as to what that means, since he seems to more or less assume his readers know.

There are two major schools of thought on this. Our charismatic friends tend toward equating the filling of the Spirit with speaking in tongues. I don't believe that they are correct on that because:

• Not everyone has the gift of tongues (1 Cor. 12:30), but everyone is commanded to be filled with the Spirit (Ephesians 5:18).
• While tongues is mentioned as evidence of being filled with the Spirit in Acts 2 and a couple other places in Acts, here in chapter 4, there is no mention of anyone speaking in tongues. Nor is tongues described as "the filling of the Spirit" elsewhere it is mentioned. For example, in Ephesians 5:18ff, evidence of filling of the Spirit includes such things as "speaking to one another with songs, hymns, and spiritual songs," avoiding drunkenness, thankfulness to God, having a God-honoring marriage, a God-honoring master/slave relationship, and obeying one's parents.
  
• Therefore, I think the filling of the Spirit, while it may be evidenced by tongues speaking, is not equivalent to it.
  

As far as I have been able to discern it biblically, the filling of the Spirit is a repeatable experience of believers that results from their rejection of and repentance from sin and choosing submission to God instead. The Spirit's filling is simply the turning over of control of your life from yourself and your flesh to God and His indwelling Spirit, so that your life produces the fruit of the Spirit (Gal. 5:22-23). I say it is repeatable, because while there are indications that the Holy Spirit's filling can be lost, or at least masked due to grieving (Eph. 4:30) or quenching (1 Thess. 5:19), it is also true that we who believe in Christ cannot lose His indwelling presence (Rom. 8:9-11).

That fact is a great comfort to me, because I find myself so often in need of fresh filling from the Spirit to accomplish the calling He has given me. Whether in my role as pastor, or as husband, father, or simply as a human being created in God's image, I often fail. I don't always speak as I should, think as I should, or act as I should. Yet God is gracious, granting both forgiveness and fresh filling from the Spirit as often as I fall down. What a mighty, gracious, compassionate God we serve!