What did Paul say would happen if he put converts back under the law?
Paul said that if he told his converts he had been wrong and put them back under the law, he would be building again that which he had destroyed. The old economy had been done away with and nailed to the cross, so returning to it would rebuild what he had torn down.
Les teaches that Paul, in Galatians chapter 2, helped believing Jews like himself see that the old economy had been totally done away with and nailed to the cross. Paul then says that if he came back and told these converts he was wrong and had to put them back under the law, he would be building again what he had destroyed. Les connects this to Colossians 2:14, where the work of the cross blotted out the handwriting of ordinances that was against us—the law, a compilation of 613 rules and regulations contrary to human nature. Returning to that law would rebuild what Paul had torn down.
For if I build again the things which I destroyed, I make myself a transgressor.