The verse is teaching that the law doesn't save, grace does.
For by grace are ye saved through faith; and that not of yourselves: it is the gift of God: Eph 2:8
And faith comes by hearing the voice of the Son of God,
Let's see, I will raise up a prophet from amongst the brethren and put My word in that Prophets mouth, then you hear what is written in in John 5:25?