What does being filled with the Spirit mean?

Tim Keller offers his thoughts:

The first place in the New Testament that discusses the work of the spirit at length is in the gospel of John. Jesus considered the teaching so important that he devoted much time to it on the night before he died. When we hear of ‘spiritual filledness,’ we think of inner peace and power, and that may indeed be a result. Jesus, however, spoke of the Holy Spirit primarily as the ‘Spirit of Truth’ who will ‘remind you of everything I have said to you’ (John 14:17,26). The Holy Spirit ‘will bring glory to me by taking from what is mine and making it known to you’ (John 16:14). What does this mean?

‘Make known’ translates a Greek word meaning a momentous announcement that rivets attention. The Holy Spirit’s task, then, is to unfold the meaning of Jesus’s person and work to believers in such a way that the glory of it – its infinite importance and beauty – is brought home to the mind and heart. This is why earlier in the letter to the Ephesians, Paul can pray that ‘the eyes of your heart be enlightened’ (1:18), that they might ‘have power…to grasp how wide and long and high and deep is the love of Christ…’ (3:17-18). The Holy Spirit’s ministry is to take truths about Jesus and make them clear to our minds and real to our hearts – so real that they console and empower and change us at our very center.

To be ‘filled with the Spirit,’ then, is to live a life of joy, sometimes quiet, sometimes towering. Truths about God’s glory and Jesus’s saving work are not just believed with the mind but create inner music (Ephesians 5:19) and an inner relish in the soul. ‘Sing and make music in your heart to the Lord, always giving thanks to God the Father for everything, in the name of our Lord Jesus Christ…’ (verses 19-20). And because the object of this song is not favorable life circumstances (which can change) but rather the truth and grace of Jesus (which cannot), this heart song does not weaken in times of difficulty.