... that you may be filled with all the fullness of God
Paul the Apostle was very fond of the word 'fullness'. He tells us that the fullness of Deity ("Godness") dwelt in Jesus Christ. (Colossians 2:9 and 1:19) He tells us also that the fullness of Christ dwells in the Church. And here in Ephesians, Paul prays that believers in Jesus will become mature in their faith so that they will be filled with the 'fullness of God'.
That is mind-boggling! The word fullness means completeness, you don't add anything more to it. So how can a Christian be filled with ALL the fullness of God? It is easy for us to think of Jesus being filled with God's fullness, but me, an ordinary Christian?
Well, here are some things to note. First of all, this 'fullness' is given to us (see Colossians 2:10) It is God's gift — complete salvation. Then Paul wants us to enjoy this fullness more and more. The Christian life is a full life — as Jesus himself says "I came that they (believers) may have life and have it to the full." (John 10:10) It is in John's Gospel that we have another reference to this word fullness (otherwise we only find it i Paul's writings in the Bible). It is in John 1:18 where we read "And from (Jesus') fullness we have all received grace upon grace".
The Christian life is a complete, abundant life, the gift of a loving gracious Saviour. No wonder Paul goes on to say in Ephesians 3:21: "to him be glory in the Church and in Chris Jesus throughout all generations, for ever and ever. Amen!"