Raba objected: [If the dying person assigned] part [of his property] to the first, and all of it to the second, [and then recovered,] the first acquires, but not the second! But Raba said, This is R. Jose's reason: It is a preventive measure, on account of the gift of Beth Horon. It was taught: If one declares his field hefker: he can retract within the first three days, but not after.