Bechorot 32 - The Sages are Alive After Death
The limitations on selling the meat of a firstborn animal apply to selling the meat of the animal tithe as well. There is, however, a problem with this rule: animal tithe scannot be sold at all! Rav Sheshet pondered the problem in the evening but resolved it the next morning: it is talking about tithes left to the orphans by their father!
Rav Idi, the assistant of Rav Sheshet, repeated this explanation without mentioning the author, and Rav Sheshet was upset. But why? If they repeat a true teaching, it should be enough! However, in the Song of Songs we have the verse, "The utterance of your palate is like a choice wine; it goes to my Beloved with sincerity, stirring the lips of those who sleep (in the grave)." When someone quotes a teaching in a sage's name, his lips stir in the grave. Of the three souls, the lower one stays in the grave and assumes the form of the body.
The orphans were given this special dispensation to protect their financial interests. However, all others have a loophole: they give the meat as a present, and ascribe the charge to the hoofs or horns.
Art: Walter Langley - The Orphan