Talmud for Shevuot 6:12

MISHNAH: Somebody exchanged a cow for a donkey and it gave birth, or he sold his slave girl and she gave birth. If one said, [it happened] before I sold, the other said, after I bought, they shall split²⁰If neither of them has proof.. If he had two slaves, one adult and one young, or two fields, one large and one small. The buyer says, I bought the large one, and the seller says, I do not know: he acquired the large one²¹Even if neither of them has proof, judgment has to be given to the one who claims certainty against one who asserts uncertainty.. The seller says, I sold the small and the other party says, I do not know: he has only the small one²¹Even if neither of them has proof, judgment has to be given to the one who claims certainty against one who asserts uncertainty.. If one says the large one and the other says the small, let the seller swear that he sold the small one²²Both assert their claim with certainty and neither of them has proof. Since the buyer did not yet enter into possession, the seller may substantiate his claim by an oath.. If both say, I do not know, they shall split²³Since neither of them asserts his claim as certain, the rule applies that “money in doubt has to be split evenly” (Chapter 1, Note 5)..