Question: "What does it mean to comprehend the "breadth and length and height and depth" in Ephesians 3:18?"
Answer: In Ephesians 3, Paul expresses his desire and prayer for the believers in Ephesus. Part of what he prays for is “that Christ may dwell in your hearts through faith—that you . . . may have strength to comprehend with all the saints what is the breadth and length and height and depth, and to know the love of Christ that surpasses knowledge, that you may be filled with all the fullness of God” (Ephesians 3:17–19, ESV). Paul here is explaining that, although he was suffering for the sake of the gospel (verses 1, 13), it was worth it if they could only grasp the magnitude of Christ’s love for them.
The Greek word translated as “comprehend” or “understand” implies more than a mental understanding. It literally means “to take hold of something and make it one’s own.” In order for the Ephesian Christians to truly understand the “love that surpasses knowledge,” they needed to go beyond hearsay. This kind of comprehension is experiential. It requires us to take hold of a truth and define ourselves by it. Paul was encouraging them—and all saints everywhere—to meditate on what it means to be fully loved by God for the sake of Christ. He wanted them to grasp God’s love in all its fullness; to know “how wide and long and high and deep is the love of Christ.”
Jesus had already defined love as it was demonstrated by both Father and Son. Of Himself He said, “Greater love has no one than this: to lay down one’s life for one’s friends” (John 15:13). Of the Father He said, “God so loved the world that He gave His only begotten Son” (John 3:16). God’s love is all-encompassing, far exceeding our ability to comprehend. Its breadth and length and height and depth are staggering. It requires meditation, soul-searching, and honesty in order to draw near enough to God to comprehend His nature (James 4:8). And that was what Paul urged them, and all Christians, to do: consider the breadth and length and height and depth of the love of Christ for His church. Later in his epistle, Paul again alludes to the love of Christ when he urges husbands to love their wives in the same way Christ loves the church (Ephesians 5:25–27).
Paul’s use of dimensional language to describe the love of Christ suggests a vastness to Christ's love. The Redeemer's love for His people is so great, of such magnitude, as to be almost beyond comprehension. The four-fold description of length-width-height-depth carries with it shades of Psalm 103:11–12, which also uses dimensional language:
"For as high as the heavens are above the earth,
so great is his love for those who fear him;
as far as the east is from the west,
so far has he removed our transgressions from us."
There is absolutely nothing at all that can separate us from the love of God in Christ (Romans 8:38–39). When we learn to bask in that love (1 John 3:1), celebrate His delight in us (Psalm 37:23), and rest in His faithfulness (Psalm 136:1), we enjoy relationship, not religion. Only a relational God could love us so much that we can barely comprehend the breadth and length and height and depth of it.