A Snake’s gift was rejected because it was presented by mouth.
A Serpent brought the gift of a rose to Jupiter who refused the gift as accepting it would put him in debt to a Serpent. Not a good thing.
If you receive a gift you must befriend the giver.

L’Estrange version
Jupiter had presents made him upon his wedding-day, greater, or less, from all living creatures. A serpent brought him a rose in his mouth for an offering. The thing was acceptable enough, but not the presenter; for (says Jupiter) though gifts are wellcome to me, of themselves, I must not yet receive any from a serpent.
Moral
He that receives a present, contracts an obligation; which a body would be asham’d of in the case of an ill man; for it looks toward making a friendship with him.

Chambry (Zeus and the Snake)
Note: The Chambry collection is published in Greek. AI was used to translate the Greek to this text:
When Zeus was marrying, all the animals brought gifts. But the snake, crawling, took up a rose in its mouth and came up. Seeing it, Zeus said: “From all the others I accept gifts even from their feet; but from your mouth I will not take anything.”
The tale shows that the favors of all wicked creatures are fearful.

How do you think an AI might simplify this fable? Here is one answer, and the illustration above was made from this simplification:
The Snake’s Gift
When mighty Zeus prepared for his wedding feast, every creature came bearing gifts. The birds brought songs, the deer offered golden fruit, and the bear carried sweet honey. At last, the snake crept forward with a bright red rose clutched in its jaws. Zeus looked down and said, “I will take gifts from every hand and even every foot—but never from your mouth, for poison hides behind your beauty.”
Moral
Even the finest gift from a wicked heart must be refused.
Perry. #221