That saying would be more truthful if the word "but" was changed to "and". Our savior did not take away the guidance the Father gave us with the law, but he perfected it. Christ said "you have been told" and then he explained that law ad it is in the spirit of the law given in our hearts as Christ said "but I tell you".
You have but to ask, and it shall be given to you...
"The law shows our sin, and the gospel shows our Savior."
Let me know if you need me to make any more changes in order to be more truthful.