For if that first covenant had been faultless, then should no place have been sought for the second . In that he saith, A new covenant, he hath made the first old. Now that which decayeth and waxeth old is ready to vanish away. It is that simple. We cannot add law to law, observance to observance.
Christians often make mention that a testament can be changed.
Likewise also the cup after supper, saying, This cup is the new testament in my blood, which is shed for you. And for this cause he is the mediator of the new testament, that by means of death, for the redemption of the transgressions that were under the first testament, they which are called might receive the promise of eternal inheritance. Whereupon neither the first testament was dedicated without blood. The law kills. The two concepts are mutually exclusive.