Translation:Shulchan Aruch/Choshen Mishpat/234

Paragraph 1- If one slaughtered a first born and sold it and it was known he did not show the animal to an expert, what was consumed was consumed, and the seller must return the money. Whatever meat is left in the buyer’s possession must be buried and the seller would return the money.

Paragraph 2- Similarly, if one slaughters a cow and sells it, and it was discovered to be a treifah, what was consumed was consumed, and the seller must return the money. Any meat the buyers did not consume would be returned and the seller would return the money. If the buyer sold this treifah meat to a gentile or fed it to the dogs, they should appraise with the butcher how much was received for the treifah and the butcher would return the rest. This rule applies to anyone who sells something that is biblically prohibited to be eaten.

Paragraph 3-  If one sells something to another that is rabbinically forbidden to be eaten, however, if the fruits were still in existence the buyer would return the fruits and take back his money, and if the buyer already consumed them, what was eaten was eaten and the seller would not return anything to him. If one sold an animal that was not properly checked to another, it is as if it was rabbinically prohibited because the requirement to check is rabbinic.

Paragraph 4- In a case of something that one is prohibited to receive benefit from, whether the prohibition is biblical or rabbinical, the seller would return the money and there would be no sale at all.