Strength Through Union With Christ

“Finally, be strong in the Lord and in the strength of his might.” – Ephesians 6:10

The strength that sustains us in spiritual battle is not a principle. It is not an emotion. It is not even a power that exists separate from a Person. The strength we are commanded to receive in Ephesians 6:10 is found in Christ Himself. “Be strong in the Lord,” Paul says. Not near Him. Not simply inspired by Him. In Him.

There is no more important distinction in the Christian life than this, that we are not merely followers of Christ, we are united to Him. Our strength does not flow from Christ as if He were a distant reservoir to be drawn upon in times of need. Our strength flows because Christ lives within us and we live within Him. This is the doctrine of union with Christ, and it is the marrow of Christian existence. It is not an accessory truth, it is the very core of who we are.

Paul has already laid this foundation throughout Ephesians, especially in the early chapters. Over and over again, he has used the phrase “in Christ”, in Him we were chosen, redeemed, adopted, sealed, raised, seated. It is not by imitation but by union that we live. We were dead, but He made us alive together with Christ (Eph. 2:5). We were raised up with Him and seated with Him in the heavenly places (Eph. 2:6). And now, having been seated and having learned to walk, we are called to stand, but only in Him.

This is not metaphor. It is not a feeling of closeness. It is a spiritual reality. Every believer is mystically, truly, unbreakably joined to Christ by faith. Just as the branch cannot live apart from the vine, the Christian has no life, no strength, no fruit, no victory apart from union with Christ (John 15:5). “Apart from Me,” Jesus said, “you can do nothing.” Nothing. Not a little less. Not somewhat poorly. Nothing.

So when Paul calls us to be strong in the Lord, he is not commanding us to reach toward Christ for strength, he is calling us to abide in the One who is already ours. It is a strength that comes not by striving, but by resting in what is already true. We do not need to manufacture our closeness to God; we need to believe it. We do not need to earn the right to draw near; we need to remember that we are already in Christ, and that His strength flows through that living connection.

The Puritans understood this well. They wrote with profound clarity on the nature of our union with Christ. Thomas Goodwin, one of the most insightful among them, wrote that the believer and Christ are so united that “Christ cannot be in heaven and you be in hell; it is impossible, because you are one with Him.” Our spiritual location, in Christ, is more real and more enduring than our earthly address.

The strength that Paul speaks of is resurrection strength, but it is not reserved for some future resurrection day. It is the very strength that now enlivens and empowers the soul. As Paul prayed earlier in this same letter, that the eyes of our hearts might be enlightened to know:

“…what is the immeasurable greatness of his power toward us who believe, according to the working of his great might that he worked in Christ when he raised him from the dead…” – Eph 1:19-20

This means that every spiritual resource needed for standing firm has already been secured for us in the person and work of Christ. He is not merely the Giver of strength, He is our strength. To be in Christ is to be anchored in unshakable victory, to be supplied with invincible life, to be armed with divine power.

But we must also be honest: though this strength is real, it is not automatic. Though it is available, it is not passive. The command to be strong in the Lord is a call to active dependence. Union with Christ does not mean we do nothing; it means we do everything in conscious reliance upon Him. We must abide. We must remain. We must dwell.

And that abiding looks like something. It looks like rising early to meet with Him in prayer, not as a duty but as a lifeline. It looks like opening the Word and feeding our souls on promises that are blood-bought and Spirit-breathed. It looks like casting our anxieties on Him rather than bearing them silently. It looks like confessing our sin quickly and receiving the strength that comes from cleansing. It looks like speaking to our own souls when they are faint: “Why are you cast down, O my soul? Hope in God!” It looks like walking through suffering, weakness, persecution, temptation, and warfare, not with gritted teeth, but with eyes fixed on the One who has overcome.

It is only when we know that we are in Christ that we can obey the call to stand. Otherwise, we will either despair or pretend. We will collapse under the weight of trials or construct a façade of strength that cannot endure the winds of affliction. But when we are rooted in Christ, when we truly grasp that our strength is not our own, we are freed from both pride and fear. We do not need to prove ourselves. We need only to abide.

This is what separates the worldly strong from the spiritually strong. Worldly strength isolates; spiritual strength abides. Worldly strength exhausts; spiritual strength renews. Worldly strength exalts self; spiritual strength exalts Christ. And so, we return to Paul’s words and we hear them again, not with familiarity but with fresh reverence: “Be strong in the Lord.” This is not just instruction, it is invitation. It is a call to live the Christian life from the only place it can truly be lived: in Christ, by Christ, through Christ, and for Christ.