Here Paul expresses his confidence in his standing with God. It is because of what his life demonstrated, just as with the Corinthians he mentioned in the previous verses (1-3).
This was not a claim of self-sufficiency. He knew that he alone was incapable of acceptably serving the Lord. He was a creature who relied upon God’s grace, as do we all. As such he wrote that he did not “think of anything as being from ourselves, but our sufficiency is from God” (5).
His sufficiency was given to Him by God. His sufficiency was as a minister of the New Covenant. In parallel, the New Covenant is sufficient. There is a significance in his comparing the “letter” to the “Spirit.” The letter kills (here referring to the Old Law). The Spirit gives life. Paul’s continued battle was to deliver the redemptive work of Christ into the lives of those who needed life, but had not found it. It is not in the Old Covenant. It was solely through Christ and His work. “The Spirit gives life” (3:6).
