βAs the truth of Christ is in meβ¦β (II Cor.Β 11:10).
Look how often Paul, in his letters, speaks with an oath: βGod is my witnessβ (Rom. 1:9), βAs God is trueβ (II Cor.Β 1:18), βBehold, before God, I lie notβ (Gal.Β 1:20), βGod is my recordβ (Phil. 1:8), βI speak the truth in Christ, and lie notβ (I Tim. 2:7), etc., etc.
As Dean Howson has said: βWhen Paul makes a solemn statement under the sense of Godβs presence, he does not hesitate to express this.β
But had not others spoken under the sense of Godβs presence? Of course they had, yet Paul calls God to witness far more often than any other Bible writer. Why is this? The answer is found in the distinctive character of Paulβs ministry as the apostle of βthe mystery.β John the Baptist, the four evangelists and the twelve apostles did not need to speak with oaths since they proclaimed that which had already been prophesied. But with Paul it was different. Separate from the twelve, who were widely known as the apostles of Christ, Paul had been raised up to make known a wonderful secret which God had kept hidden from all who had gone before. While not a contradiction of prophecy, this secret had nevertheless not been prophesied; it was a new revelation. Hence it was appropriate that the Apostle should insist again and again that he wrote as in the presence of God.
As we consider Paulβs oaths, however, we must ask ourselves whether anyone ever used the oath with more solemn sincerity. Did anyone ever suffer so intensely for the truths he proclaimed, or pay so dearly to convince others of them? Could anyone say with such simplicity to those who knew him best:
βYe knowβ¦ after what manner I have been with you at all seasons, serving the Lord with all humility of mind, and with many tears and temptations [testings]β¦ and how I kept back nothing that was profitable unto youβ¦β (Acts 20:18-20). source