Colossians 1:24-29

It was too small a thing for Jesus to come only  for the Jews, now Jew and Gentile are united in one body, the Body of  Jesus Christ our Lord.

Ephesians 3:1 For this reason I, Paul, the prisoner of Christ Jesus for you Gentiles—

He did not leave us here alone but instills the very heart of God,  Holy Spirit , in us to teach us all things. He gives, not head knowledge, but heart knowledge  behind the teachings of  Jesus Christ. Out of His heart we speak of the salvation, the Good News, that the  Father  offered to the world. Through His power and His grace we use these truths for the good of mankind and the Body of Christ, His Church.

Moses reminded the Israelites of the foundational commandment to love the Lord with all their heart, soul and might, not just with a portion of themselves. But what did it mean for the Israelites to love the Lord with their entire being?

Different Bible translations use the word "mind" or "heart" for the Hebrew word levav, which literally means they were to love the Lord with the inner part of who they were.

Moses further instructed them to love the Lord with all their soul, or nephesh. They were to faithfully love the Lord with every breath they inhaled and exhaled.

The commandment concludes with Moses instructing the Israelites in their complete and total commitment to the Lord as they loved Him with all their might, strength or power.

In Mark 12:29-30, Jesus identified the Shema as the most important command in Scripture ... and, more than that, He is the only person who has ever truly fulfilled this command, pouring out all His heart, soul and strength in perfect love to redeem us (Romans 3:23-24). Then He gave us His Spirit to indwell us and help us in our times of weakness (Romans 8:26). By God's grace and by His Spirit's power, we seek to honor God by loving Him as He commanded. First5 

Shemaʿ (Heb., ‘hear’). Declaration of God 's unity in the Jewish liturgy.

Colossians 1:24-29

24 I now rejoice in my sufferings for you, and fill up in my flesh what is lacking in the afflictions of Christ, for the sake of His body, which is the church, 25 of which I became a minister according to the stewardship from God which was given to me for you, to fulfill the word of God, 26 the mystery which has been hidden from ages and from generations, but now has been revealed to His saints. 27 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. 28 Him we preach, warning every man and teaching every man in all wisdom, that we may present every man perfect in Christ Jesus. 29 To this end I also labor, striving according to His working which works in me mightily. The New King James Version

In this verse, Paul is not saying that Christ’s death was insufficient or that somehow he was a coredeemer with Christ. Paul is making the point that a Christian will endure the sufferings that Christ would be enduring if He were still in the world. Christ had told His disciples that if the world hated Him it would hate His followers. If people persecuted Him they would persecute His followers. 

Paul believed he was suffering the afflictions God wanted him to endure. Instead of facing his difficulties with dread, Paul saw his troubles as a time of joy, because they were producing an eternal reward. 

In Greek pagan religions, a mystery was a secret teaching reserved for a few spiritual teachers who had been initiated into an inner circle. Paul uses the word to refer to knowledge that had been hidden from ages and from generations but was now being revealed by God. The Lord had revealed this mystery to Paul and called him to be a steward of it.

The mystery is that Christ now lives within Gentile believers: Christ in you, the hope of glory. This is in harmony with Ephesians. In that letter, Paul states that the mystery is the union of Jews and Gentiles in one body, Christ’s church. 

The concept of perfection in the NT means completeness or maturity. Here the reference is probably to the coming of Christ, when every believer will experience the completion of Christ’s work in him or her. The NKJV Study Bible

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’s Concise Commentary

Romans 8:10 And if Christ is in you, the body is dead because of sin, but the Spirit is life because of righteousness.

1 Corinthians 2:7 But we speak the wisdom of God in a mystery, the hidden wisdom which God ordained before the ages for our glory,

1 Corinthians 15:10 But by the grace of God I am what I am, and His grace toward me was not in vain; but I labored more abundantly than they all, yet not I, but the grace of God which was with me.

2 Corinthians 1:5 For as the sufferings of Christ abound in us, so our consolation also abounds through Christ.