The source of this expression is Paul of Tarsus, who uses it in 2 Cor. 12:7-10: To keep me from becoming conceited because of these surpassingly great revelations, there was given me a thorn in my flesh, a messenger of Satan, to torment me. Three times I pleaded with the Lord to take it away from me. But he said to me, "My grace is sufficient for you, for my power is made perfect in weakness." Therefore I will boast all the more gladly about my weaknesses, so that Christ's power may rest on me. (NIV) Many interpretations have been given of Paul's meaning: