Courtesy is still in fashion in heaven. Courtesy is still something that God likes to see — so be courteous, tactful, and sensitive in the living of the Spirit of God.
God took the divine risk of creating beings who could say “no” to Him. And then He made plans to redeem them and make them once again part of His heavenly family.
Now about this matter of a mystery, it doesn’t represent something you cannot know. When the Bible uses the word mystery, it’s something that you can’t know by yourself but which God wants to open up to you.
Yes, He said He has raised us up together, made us sit together in the heavenlies that in the ages to come He might show the exceeding riches of His grace. So then what are the riches of His grace?
There is principality and there is power and there is might and there is dominion and there is the precedence of one name over another, every name that is named but the Lord Jesus tops it all.
What is the hope of His calling? It boils down to this. God wants to see something happen as a result of His having called you to Himself. He did this with something in mind.