What Is Union With Christ?

by Cale Fauver July 3, 2019

The Heart of the Christian Life

Scottish theologian Sinclair Ferguson once wrote that, "[union with Christ is] a doctrine which lies at the heart of the Christian life." If there was ever a doctrine taught so profoundly in the Scriptures that believers must better see and adore, it is their union with Christ. 

And yet, I find that we need a helpful understanding and a clear picture of this profound mystery that is the core of the gospel of God. First, I want to look at the language of what it means to be united to Christ in the New Testament, and then I want to take you to a beautiful picture of what this looks like in the Old Testament.

New Testament Shorthand

If by his mercy, God has caused to be born again (1 Peter 1:3) and you have turned from your sins and believed the gospel (Mark 1:15), then God has placed your sin, debt, and life of rebellion upon Jesus Christ on Calvary's tree and crushed his Son. And by faith, God then takes the righteousness of Christ's full and active obedience to the Lord God and credits it, or imputes it, to your account. 

We may not have seen it, but we have repeatedly read and reread the New Testament shorthand language for this truth, which is used at least 164 times in Paul's letters alone, according to John Stott:

– "There is therefore now no condemnation for those who are in Christ Jesus." (Romans 8:1)

– "Therefore, if anyone is in Christ, he is a new creation. The old has passed away; behold, the new has come." (2 Corinthians 5:17)

– "For our sake he made him to be sin who knew no sin, so that in him we might become the righteousness of God." (2 Corinthians 5:21)

– "even as he chose us in him before the foundation of the world, that we should be holy and blameless before him. In love," (Ephesians 1:4).

Likewise, we see not only are we called "in Christ" but we see that Christ is also in us:

– "To them God chose to make known how great among the Gentiles are the riches of the glory of this mystery, which is Christ in you, the hope of glory." (Colossians 1:27).

– "But if Christ is in you, although the body is dead because of sin, the Spirit is life because of righteousness." (Romans 8:10)

And sometimes we see both in the same text:

– "By this we know that we abide in him and he in us, because he has given us of his Spirit." (1 John 4:13)

– "I have been crucified with Christ. It is no longer I who live, but Christ who lives in me. And the life I now live in the flesh I live by faith in the Son of God, who loved me and gave himself for me." (Galatians 2:20)

– "Abide in me, and I in you. As the branch cannot bear fruit by itself, unless it abides in the vine, neither can you, unless you abide in me." (John 15:4)

This union means this: you identify with Christ and he with you. His life is your life, his death is your death, and his resurrection is your resurrection — or as Paul writes in Romans 6:5, "For if we have been united with him…"  Believer you were chosen in Christ, made alive together with Christ, counted righteous in Christ, hidden in Christ, baptized into Christ, and will one day be glorified with Christ. Friends, this is why we shall not live in our sin. We have died to sin in his death and are now alive to God in his resurrection. By Adam's disobedience, we became sinners; and so by Christ's obedience we have been made righteous (Romans 5:19).  How we can who died to sin still live in it? (Romans 6:1-2). Open to Romans 5:18-6:11 and your soul will fly to heavenly heights laden with imperishable gold.

Old Testament Portrayal

I love the Old Testament, and I was re-reminded of this beautiful doctrine of our union with Christ upon reading 1 Samuel 18:1-4 which says:

"As soon as he had finished speaking to Saul, the soul of Jonathan was knit to the soul of David, and Jonathan loved him as his own soul. And Saul took him that day and would not let him return to his father's house. Then Jonathan made a covenant with David, because he loved him as his own soul. And Jonathan stripped himself of the robe that was on him and gave it to David, and his armor, and even his sword and his bow and his belt."

Beloved brothers and sisters, do you see the love of the Son for you and his voluntary uniting of himself to you? The Lord Jesus "knit" himself to you and he loves you "as his own soul." You are one with the everlasting Son of God. How? Christ Jesus "made a covenant with [you], because he loved [you] has his own soul." You are united to Christ, or in a covenant relationship with him — as the one-flesh union of a husband to his bride (see Ephesians 5:25-32). Jonathan then takes is own robe "that was on him and gave it to David, and his armor, and even his sword and his bow and his belt." 

There wasn't exactly a Wal-Mart in Israel where you could shop the clearance aisle and gathering some extra robes and armor and swords and belts. These are precious and personal pieces of equipment. Every time someone would see David dressed and armed in Jonathan's weapons they would recognize them as Jonathan's even though they are David's. And every morning, David would put on Jonathan's robe and sword knowing that these are Jonathan's, but are now his own — we see the same Old Testament theme with Joseph in Genesis 41:42 and with Mordecai in Esther 6:8.

His life, yours. His righteousness, yours. His Father's favor, yours. His resurrection, yours. His holiness, yours. His love of the Father, yours. You are knit together with Christ.

One with Himself I cannot die
My soul is purchased by His blood
My life is hid with Christ on high
With Christ my Savior and my God!
With Christ my Savior and my God!