5. In the same light are we to consider the law of the Decalogue, delivered by God to His peculiar people, the Jews, by the hands of Moses. For though it reveals the greatness of sin, and more and more convinces man thereof, yet, as it neither points out a remedy nor imparts strength to extricate him from his misery, but, being weak through the flesh, leaves the transgressor under the curse, and man cannot by this law obtain saving grace.
6. What, therefore, neither the light of nature nor the law could do, that God performs by the operation of the Holy Spirit through the word or ministry of reconciliation; which is the gospel concerning the Messiah, by means whereof it has pleased God to save such as believe, as well under the Old as under the New Testament.
Synod of the Reformed Church (1619), Canons of Dort 3/4.5–6
Jesus however referred to the Shema. Which along with His “But I say to you”, increased the revelation to us of our sinfulness, it being an impossible condition of life, we not even being able to perfectly obey His second, like commandment.
What is impossible for us, God has given us in Christ. That is the glorious good news, the covenant of grace that was inaugurated in the garden and sealed by the blood of Christ. When we believe this, we begin to love God and neighbour. The law becomes precious to us because it shows us how to please Him. The Holy Spirit works this in us by the means of the preaching of the word and the use of the sacraments.