John Calvin Commentary Colossians 2:7

"rooted and builded up in him, and established in your faith, even as ye were taught, abounding in thanksgiving." — Colossians 2:7 (ASV)

And confirmed in the faith. He now repeats without figurative language the same thing that he had expressed through metaphors: that continuance in the way, the support of the root, and of the foundation, is the firmness and steadfastness of faith. And observe that this argument is presented to them because they have been well instructed, so that they may safely and confidently secure their footing in the faith which they had come to know.

Abounding. He does not want them simply to remain immovable, but wants them to grow more and more each day. When he adds, with thanksgiving, he wants them always to keep in mind the source from which faith itself comes, so that they may not be puffed up with presumption, but may instead, with reverence, rest in the gift of God. And, undoubtedly, ingratitude is very often the reason why we are deprived of the light of the gospel, as well as of other divine blessings.