What does Ephesians 3:19 mean?

Paul wants his readers to experience the love of Christ in a way that goes beyond mere information. This does not imply that knowledge is unimportant. Instead, Paul wants the Ephesians to understand that God's love is ultimately beyond our comprehension. We will never completely understand it. Echoing the sentiment of James, he suggests that true, godly love is not limited to mere knowledge; it must be expressed in action (James 2:17–23). Paul called love "the greatest of these [gifts of God]" (1 Corinthians 13:13). Scripture often speaks of God's love, saying "God is love" (1 John 4:8).

In contrast, the Pharisees were said to follow the law, in their actions, yet neglected the "love of God" (Luke 11:42) and did not have the love of God in them (John 5:42). So, action without love is just as invalid as love without action.

Paul's desire for his readers to grow in God's love has a specific purpose. This "fullness of God" is mentioned only one other time in Scripture, in Colossians 1:19: "For in [Jesus] all the fullness of God was pleased to dwell." There, the focus is on the greatness of God which exists in Jesus, clearly labelling Jesus as divine. In a similar manner, Paul wants his audience to be filled with Jesus as much as possible. He knows that love, in both thoughts and actions, is the key to this taking place in the life of a believer (Ephesians 3:18).