In chapter 3 Paul compared the letters of recommendation that the false apostles were using to authenticate themselves and attempt to discredit Paul, to the changed lives that the people represented. Nobody can argue with a changed life and there is a reason that testimonials are used for commercials, advertising, and weight loss. When people see someone with the same struggle is able to overcome it, they have hope and are willing to try. Paul told them that they themselves were like living letters testifying of not only his discipleship of them, but of Christ Himself. He also takes this comparison another step by comparing the stone tablets of the law to the spirit of God because the law was not sufficient to cleanse sin, it only convicted of sin and made us aware, but the Son of God died and cleansed us from sin and His Spirit, not the law is what changes us from the inside out. We aren’t changed by simply knowing what is wrong. We are changed when the Spirit comes in and changes our hearts. This is why Paul reminds them (and us) that our confidence is in Christ and not ourselves. Paul did not need letters of recommendation to prove that he was a legitimate apostle. His confidence was in Christ so the churches he started flourished and grew all over the place because what is of God will grow. If our confidence is in God, we will need nobody to affirm us, but we will grow and flourish so much that the change in us will be evident to all. Paul used one more comparison when he talked about Moses using a veil over his face to speak to the people because immediately after talking to God his face would be changed and he would glow for a while until the glory of God faded from his face. The people could not handle the glory of God and they didn’t understand it just as the Jews are unable to see the fulfillment of Scripture points to Jesus as the Messiah until the day that God unveils their eyes. We are this way too without the Spirit of God. When Jesus sent us “the comforter” in his place he promised to guide us into truth. There are things that we can only see by the revealing of the Holy Spirit. There are things we can only understand when the Holy Spirit teaches us. There is truth that will only come to light when Holy Spirit shines a light on it, and spiritual gifts activated only by the Holy Spirit. This is why Paul said the letter, or the law kills (because we will literally die trying to fulfill it) but the Spirit gives life. We need the Holy Spirit to lead, guide and teach us because our confidence is not in ourselves or the law, but in Christ.