Read 2 Corinthians 4:7 Using Other Translations
But we have this treasure in earthen vessels, that the excellency of the power may be of God, and not of us.
But we have this treasure in jars of clay, to show that the surpassing power belongs to God and not to us.
We now have this light shining in our hearts, but we ourselves are like fragile clay jars containing this great treasure. This makes it clear that our great power is from God, not from ourselves.