Albert Barnes Commentary Luke 10:26

"And he said unto him, What is written in the law? how readest thou?" — Luke 10:26 (ASV)

What is written, and so on. Jesus referred him to the law as a safe rule and asked him what was said there. The lawyer was doubtless endeavoring to justify himself by obeying the law. He trusted in his own works. To lead him away from that ground—to make him feel that it was an unsafe foundation—Jesus showed him what the law required, and in this way showed him that he needed a better righteousness than his own.

This is the proper use of the law. By comparing ourselves with that, we see our own defects and are thus prepared to welcome a better righteousness than our own—namely, that of the Lord Jesus Christ. Thus, the law becomes a schoolmaster to lead us to him (Galatians 3:24).