"one single law, the unchangeable will of God"

     "We believe, teach, and confess that, although people who truly believe in Christ and are genuinely converted to God have been liberated and set free from the curse and compulsion [(Fluch und Zwang | maledictione et coactione)] of the law through Christ, they indeed are not for that reason without the law.  Instead, they have been redeemed by the Son of God so that they may practice the law day and night (Ps. 119[:1]).
". . . the proclamation of the law is [therefore] to be diligently impressed not only upon unbelievers and the unrepentant but also upon those who believe in Christ and are truly converted, reborn, and justified through faith."

     Formula of Concord (1577) Epitome VI (Concerning the third use of the law).1-2, trans. Robert Kolb.  There is much more of value here, and even more in Article VI of the Solid Declaration.  The headline is from Epitome VI.6:  "for both the repentant and unrepentant, for the reborn and those not reborn, the law is and remains one single law, the unchangeable will of God."