Nicene and Post-Nicene Fathers, Ser. II, Vol. XIV:
The Canons of the Synods of Sardica, Carthage, Constantinople, and Carthage Under St. Cyprian, Which Canons Were Received by the Council in Trullo and Ratified by II. Nice.: Canon CXIII

Canon CXIII.  (Greek cxiiii.)

That without the grace of God we can do no good thing.

It seemed good that whosoever should say that the grace of justification was given to us only that we might be able more readily by grace to perform what we were ordered to do through our free will; as if though grace was not given, although not easily, yet nevertheless we could even without grace fulfil the divine commandments, let him be anathema.  For the Lord spake concerning the fruits of the commandments, when he said:  “Without me ye can do nothing,” and not “Without me ye could do it but with difficulty.”

Notes.

Ancient Epitome of Canon CXIII.

Whoso preaches that without grace we could keep the commandments although with difficulty, is to be thrice execrated.  For the Lord says, “Without me ye can do nothing.”

This is Canon V. of Carthage, a.d. 418.