SurLaLune Note: This tale is from the footnotes to the previous tale, "The Ingrates," but is provided also as a separate entry for the SurLaLune database classification and searching ease.
There is also a version of this fable in Morosi, p. 75, which is as follows:--
XLIX. THE MAN, THE SERPENT, AND THE FOX.
THERE was once a huntsman, who, in passing a quarry, found a serpent under a large stone. The serpent asked the hunter to liberate him, but the latter said: "I will not free you, for you will eat me." The serpent replied: "Liberate me, for I will not eat you." When the hunter had set the serpent at liberty, the latter wanted to devour him, but the hunter said: "What are you doing? Did you not promise me that you would not eat me?" The serpent replied that hunger did not observe promises. The hunter then said: "If you have no right to eat me, will you do it?" "No," answered the serpent. "Let us go, then," said the hunter, "and ask three times." They went into the woods and found a greyhound, and asked him, and he replied: "I had a master, and I went hunting and caught hares, and when I carried them home my master had nothing too good to give me to eat; now, when I cannot overtake even a tortoise, because I am old, my master wishes to kill me; for this reason I condemn you to be eaten by the serpent; for he who does good finds evil." "Do you hear? We have one judge," said the serpent. They continued their journey, and found a horse, and asked him, and he too replied that the serpent was right to eat the man, "for," he said, "I had a master, who fed me when I could travel; now that I can do so no longer, he would like to hang me." The serpent said: "Behold, two judges!" They went on, and found a fox. The huntsman said: "Fox, you must aid me. Listen: I was passing a quarry, and found this serpent dying under a large stone, and he asked aid from me, and I released him, and now he wants to eat me." The fox answered: "I will be the judge. Let us return to the quarry, to see how the serpent was." They went there, and put the stone on the serpent, and the fox asked: "Is that the way you were?" "Yes," answered the serpent. "Very well, then, stay so always!" said the fox.