Adam Clarke on Colossians 1:9

For this cause - See on Eph 1:15-16 (note), where the same sentiment occurs.

That ye might be filled - Nothing could satisfy the apostle, either for himself or his hearers, but the fullness of the blessing of the Gospel of peace. The Colossians had knowledge, but they must have more; it is their privilege to be filled with it. As the bright shining of the sun in the firmament of heaven fills the whole world with light and heat, so the light of the Sun of righteousness is to illuminate their whole souls, and fill them with Divine splendor, so that they might know the will of God, in all wisdom and spiritual understanding; in a word, that they might have such a knowledge of Divine things as the Spirit of truth can teach to the soul of man.