Is there a slave which cannot be sold for his fine - מי איכא עבדא דלא מזדבן לקנסא
Summary:
People will not be willing to purchase an עבד (who is not worth a שוה פרוטה), even if they don’t feed him, for they do not want him being around, however if it’s only for קנס they may consider paying a פרוטה for the שלשים שקלים. Alternately, if we maintain מכרו לקנס אינו מכור, one cannot sell an עבד who is not worth a שוה פרוטה.