God wanted everyone, not just Jews, to know this rich and glorious secret inside and out, regardless of their background, regardless of their religious standing. The mystery in a nutshell is just this: Christ is in you, therefore you can look forward to sharing in God’s glory. It’s that simple. That is the substance of our Message.
Colossians 1:27 (MSG)
Both the sufferings of the Head and of the members are called the sufferings of Christ, and make up, as it were, one body of sufferings. But He suffered for the redemption of the church; we suffer on other accounts; for we do but slightly taste that cup of afflictions of which Christ first drank deeply. A Christian may be said to fill up that which remains of the sufferings of Christ, when he takes up his cross, and after the pattern of Christ, bears patiently the afflictions God allots to him. Let us be thankful that God has made known to us mysteries hidden from ages and generations, and has showed the riches of his glory among us. As Christ is preached among us, let us seriously inquire, whether he dwells and reigns in us; for this alone can warrant our assured hope of his glory. We must be faithful to death, through all trials, that we may receive the crown of life, and obtain the end of our faith, the salvation of our souls. Matthew Henry