2 Corinthians 4-5

For God, who said, "Let light shine out of darkness," has shone in our hearts to give the light of the knowledge of the glory of God in the face of Jesus Christ. But we have this treasure in jars of clay, to show that the surpassing power belongs to God and not to us. 2 Corinthians 4:6-7

Paul is assuring the Corinthian believers about the truth of the Gospel. The Gospel is all about God's glory through Jesus Christ. We as God's servants are not to try and claim glory for the effects of the Gospel in other people's lives. The truth is, none of us deserved to be rescued from our selfish, blinded life; so when we selfishly refuse to give out the Gospel - whether it's fear, sin, or apathy - the result is simply to deny life to one who desperately needs it. How can God use such sinful vessels as ourselves to show His saving glory? It's so everyone will know that salvation comes from God. We are not capable of anything in ourselves, but working and living in the power of the Holy Spirit and the Word of God can accomplish anything God wants for it. Let us never boast anything but the truth that we as sinful people are used to accomplish eternal Kingdom projects through His power.

Thus says the LORD: "Let not the wise man boast in his wisdom, let not the mighty man boast in his might, let not the rich man boast in his riches, but let him who boasts boast in this, that he understands and knows me, that I am the LORD who practices steadfast love, justice, and righteousness in the earth. For in these things I delight, declares the LORD." Jeremiah 9:23-24