Matthew 27:3-5 3 Then when Judas, his betrayer, saw that Jesus was condemned, he changed his mind and brought back the thirty pieces of silver to the chief priests and the elders, 4 saying, "I have sinned by betraying innocent blood." They said, "What is that to us? See to it yourself." 5 And throwing down the pieces of silver into the temple, he departed, and he went and hanged himself.
The legalistic view of the law, embodied here by the Pharisees, can never deliver
it can convict one of sin - cf. Rom 7
and then when one comes to it as a sinner
it replies: "So what? You deal with it"
and that's exactly what Judas does - he deals with it himself
this is all the morality and legality of the world can do (the Christless view of God's shadows)
it leads to self-death