Such A Ministry As Has Been Depicted makes Clear That Its Ministers Are Not Corrupt Because It Is Conducted In God's Glorious Light And Reveals the Unmatchable Glory of God in Jesus Christ Even Though The Bearers of the Message Are But Earthen Vessels (2 Corinthians 4:1-7).
Paul will now argue that no one could conduct such a ministry as has just been depicted unless they themselves were genuine and sincere. For it is all about the light of the glory of God and of the Lord Jesus Christ (2 Corinthians 4:4 compare 1 John 1:5-10) which shines in men's hearts so that no sin can remain hidden. How could they who look with unveiled face on the glory of the Lord be guilty of fickleness or duplicity? But he admits that they have this treasure in earthen vessels, like the earthenware lamps in their houses contain the light, so that all the glory might go to God. They are but the earthly containers of the true light. Indeed that explains why they are so insignificant in themselves
This last fact is then illustrated by the afflictions they face, which do not, however, concern them because their faith is placed firmly in the One who will raise them and present them before Him. Thus they can ignore their bodily decay, for they look forward to the eternal glory.
The section from 2 Corinthians 4:1-6 links back to 2 Corinthians 2:14-17. Once again we have reference to those who are perishing (2 Corinthians 4:3 compare 2 Corinthians 2:15); corrupting God's word (2 Corinthians 4:2 compare 2 Corinthians 2:17) under the eye of God (2 Corinthians 4:2 with 2 Corinthians 2:17); and the communication of the knowledge of God (2 Corinthians 4:6 with 2 Corinthians 2:14). But there it was the fragrance that wafted out, here it is the light.
It also refers back to chapter 3 for it expands on the idea of the light that has been veiled, a greater light than that on the face of Moses. So the whole passage is a unity.