2 Corinthians 4:7

‘But we have this treasure in earthen vessels, that the exceeding greatness of the power may be of God, and not from ourselves.'

However, although God has shined in their hearts and they therefore carry within their inner selves something of the glory of God, they do not thereby boast. For they recognise that that glory is contained in earthen vessels. The comparison is with the earthen vessel that contained the oil and the wick which gave off light in people's homes. The earthen vessel is but a cheap container, it is not itself the light. Therefore none should look at the earthen container, they should look at the light within to see whether it is genuine or not. And if they look at the light that Paul reveals he has no doubt what their decision will be.

There may also be behind this the idea of God as the potter and we as the clay. The vessels are made by God and can be broken or not as He will. It is God Who determines all that will happen to them (Jeremiah 18:1; Isaiah 45:9).