‘Having made known to us the mystery of his will, according to his good pleasure which he purposed in him, unto a stewardship (regulation of an estate) of the fullness of times, to sum up all things in Christ, the things in the heavens and the things on the earth.'
In carrying out these purposes God has made known to us the mystery of His will. This ‘mystery', the hidden wisdom from before time began that God foreordained to our glory (1 Corinthians 2:7), was kept in God's counsel through eternal ages (Romans 16:25) but is now revealed to us. And this mystery is ‘Christ in us, the hope of glory' (Colossians 1:26-27).
So the eternal mystery, which was fully purposed in the will of God from before the beginning of creation, and was kept secret until His coming, was that ‘in Christ' those chosen in Him would be taken from their sinful and dreadful state, be delivered, and be transformed into His image, enjoying in themselves the indwelling of Christ, and finally sharing with Him His glory throughout eternity, when all things are summed up in Christ.
‘According to His good pleasure which He purposed in Him unto a stewardship (regulation, management of an estate) of the fullness of times.' And this is all of God's good pleasure, His settled purpose ‘in Christ'. And His purpose is that He will act as Divine Estate Manager in the fullness of times, (all time from now until the glorious finalisation) carrying out His stewardship and regulating everything so as to bring about the summing up of all things in Christ, whether in Heaven or on earth.
‘Stewardship, dispensation'. The word oikonomia meant household management, stewardship, estate management, the dispensing (and thus dispensation) of what one controls, and the word developed to mean ‘arrangement, regulation, administration'. Here it refers to His continual management of all things through time.
‘Mystery.' (Musterion). In the New Testament this means a mystery once hidden but now revealed to His own.
‘To sum up all things in Christ.' The word means ‘to summarise, to sum up', usually in a piece of literature. So in the end the whole of history will be summed up and find its meaning in Christ, reaching its ultimate end as planned by God. As Paul tells us in Colossians 1:16-17, ‘in Him were all things created, in the heavens and on the earth, things visible and invisible -- all things have been created through Him and unto Him, and He is before all things and in Him all things hold together', and here we are told that they will all come to their final satisfactory conclusion in Him, when everything is brought together in the final summation, and when the creation itself is delivered from the bondage of corruption to the glorious liberty of the children of God (Romans 8:21) and there is a new Heaven and a new earth in which dwells righteousness, the old having been finally destroyed (1 Peter 3:12-13).