Justin Martyr: The Dialogue with Trypho - Chapter XII.—Volation of the Eternal Law.
I also adduced another passage in which Isaiah exclaims: “ ‘Hear My words, and your soul shall live; and I will make an everlasting covenant with you, even the sure mercies of David. Behold, I have given Him for a witness to the people: nations which know not Thee shall call on Thee; peoples who know not Thee shall escape to Thee, because of thy God, the Holy One of Israel; for He has glorified Thee.’ (Isaiah lv.3ff) This same law you have despised, and His new holy covenant you have slighted; and now you neither receive it, nor repent of your evil deeds. ‘For your ears are closed, your eyes are blinded, and the heart is hardened,’ Jeremiah (John xii.40; Isaiah vi.10; Jeremiah vii. 24-26, xi.8, xvii.23) has cried; yet not even then do you listen. The Lawgiver is present, yet you do not see Him; to the poor the Gospel s preached, the blind see, yet you do not understand. You have now need of a second circumcision, though you glory greatly in the flesh. The new law requires you to keep perpetual sabbath, and you, because you are idle for one day, suppose you are pious, not discerning why this has been commanded you: and if you eat unleavened bread, you say the will of God has been fulfilled. The Lord our God does not take pleasure in such observances: if there is any perjured person or a thief among you, let him cease to be so; if any adulterer, let him repent; then he has kept the sweet and true sabbaths of God. If any one has impure hands, let him wash and be pure.