From the chapter as named above in the Marrow of Modern Divinity:
Nomista. But, sir, you know, that when a covenant is broken, the parties that were bound are freed and released from their engagements; and therefore, methinks, both Adam and his posterity should have been released from the covenant of works when it was broken, especially considering they have no strength to perform the condition of it.
Evangelista Indeed it is true, in every covenant, if either party fail in his duty, and perform not his condition, the other party is thereby freed from his part, but the party failing is not freed till the other release him; and, therefore, though the Lord be freed from performing his condition, that is, from giving to man eternal life, yet so is not man from his part; no, though strength to obey be lost, yet man having lost it by his own default, the obligation to obedience remains still; so that Adam and his offspring are no more discharged of their duties, because they have no strength to do them, than a debtor is quitted of his bond, because he wants money to pay it. And thus, Nomista, I have, according to your desire, endeavoured to help you to the true knowledge of the law of works.