Summary: Christ lives in us through His Spirit
To them God willed to make known what are the riches of the glory of this mystery among the Gentiles: which is Christ in you, the hope of glory.
Other translations puts it this way :
God [in His eternal plan] chose to make known to them how great for the Gentiles are the riches of the glory of this mystery, which is Christ in and among you, the hope and guarantee of [realizing the] glory. - AMP
God did this because he wanted you Gentiles to understand his wonderful and glorious mystery. And the mystery is that Christ lives in you, and he is your hope of sharing in God’s glory. CEV
The mystery that Paul is revealing to us is that we have Christ Himself living in us and He is the hope of God's glory.
Christ abides in us and we need to always acknowledge His presence in us at all times. When we have Him in our lives He comes to live in us.
Bible references of Christ abiding in us :
Now you are the body of Christ, and members individually.
I have been crucified with Christ; it is no longer I who live, but Christ lives in me; and the life which I now live in the flesh I live by faith in the Son of God, who loved me and gave Himself for me.
Now he who keeps His commandments abides in Him, and He in him. And by this we know that He abides in us, by the Spirit whom He has given us.
That Christ may dwell in your hearts through faith; that you, being rooted and grounded in love, may be able to comprehend with all the saints what is the width and length and depth and height— to know the love of Christ which passes knowledge; that you may be filled with all the fullness of God.
At that day you will know that I am in My Father, and you in Me, and I in you.
This mystery was hidden for a long time but it as now been revealed to us all. And this was revealed to us because it was God's will to manifest His Son to us. The finished work of Jesus is the reason that God made the mystery known to us.
Christ in us is the hope of glory is so powerful and it comes with a lot of benefits, there is a purpose of Christ been in us, Christ is in us and He is there to reveal his power in us and through us.
Christ in us the hope of glory will also reveal the will of God for our lives. Through His WORD we can know God's will for our lives.
For I know the thoughts that I think toward you, says the Lord, thoughts of peace and not of evil, to give you a future and a hope.
God's thoughts towards us right now is peace, to give us a future and a hope. His will is for us is always good and not evil thoughts and this is great, that as our Father looks on us He has a smile on His face.
1 Timothy 2: 3 - 4
For this is good and acceptable in the sight of God our Savior, who desires all men to be saved and to come to the knowledge of the truth.
God's will is that everyone will be saved and will accept His Son as the Savior because He is the only truth. His will is that none will perish and that the death of His Son will not be in vain.
In everything give thanks; for this is the will of God in Christ Jesus for you.
God's will is to always thank Him in every circumstances of life.
For this is the will of God, your sanctification: that you should abstain from sexual immorality.
The meaning of sanctification is the act or process of acquiring sanctity. of being made or becoming holy. It is a gift given through the power of God to a person or thing which is then considered sacred or set apart in an official capacity within the religion.
God has set us apart and wants us to live a life that will abstain from sexual immorality because our body is the temple of the Holy Spirit.
Hebrews 13: 20 -21
Now may the God of peace who brought up our Lord Jesus from the dead, that great Shepherd of the sheep, through the blood of the everlasting covenant, make you complete in every good work to do His will, working in you what is well pleasing in His sight, through Jesus Christ, to whom be glory forever and ever. Amen.