"The light of the knowledge of the glory of God in Christ Jesus" is called a TREASURE because it is RICH TRUTH which sets men free; it has RICH BLESSINGS such as wisdom, righteousness, sanctification, and redemption; it contains RICH AND PRECIOUS PROMISES; it brings to us the RICHES OF HIS GRACE IN CHRIST.
This treasure is, "in earthen vessels," meaning the ministers to whom God entrusts this gospel and through whom He sends the gospel to His sheep. These ministers are God's men; but they are still men,weak and frail, subject to like passions and infirmities, "that the excellency of the power may be of God and not of us." Whatever is accomplished in the proclamation of the gospel by these men is the result of God's purpose and work, certainly not of us. Paul wrote in I Cor. 15:10, "I have labored more abundantly than they all; YET NOT I, but the grace of God which was with me. Therefore, whether it were I or they, so we preach and so ye believe." Let not one grain of faith be in the wisdom of any man, but in the wisdom and power of God—WHICH IS CHRIST!