en_tn/eph/03/18.md

that you might be able to understand

This is the first item which Paul says will be the result of the Christians being rooted and grounded in Christ's love (Ephesians 3:17).

all God's holy people

"all believers in Christ" or "all the saints"

the width, the length, the height, and the depth

Possible meanings are 1) these words describe the greatness of God's wisdom, Alternate translation: "how very wise God is" or 2) these word describe the intensity of Christ's love for us. Alternate translation: "how much Christ loves us" (See: rc://en/ta/man/jit/figs-metaphor)