창세기 49:32의 주석

מקנה השדה והמערה אשר בו, The purchase of the field and the cave which is in it, etc. After Jacob had alluded to the acquisition of the cave as something that was his exclusively, he repeated a particular detail which could possibly form the basis of a claim by the Hittites in the future. This was the law known in the Talmud as בר מצרא, that when a field is up for sale a person owning an adjoining field enjoys a privileged status as a potential buyer. This status is so strong that such a neighbour can force a deal which had been concluded already to be reversed in his favour.

מאת בני חת, “from the Hittites.” Yaakov repeats this although he had already spelled out that the individual from whom his grandfather purchased this field was Efron the Hittite, as Efron himself was no longer alive to confirm his claim. Seeing that Joseph also had not been present at the time when this transaction had taken place, he went into great detail so that he would know how to answer anyone of Efron’s heirs if he would dare to dispute his father’s claim.

Even though this law applies only when said field has been purchased by a Jew- as explained in Baba Metzia 108,- and the reason is that the Jewish purchaser can argue that his neighbour should be happy that he no longer has a Gentile as a neighbour, the reason given is not true. Were it true, the Gentiles could argue the same in reverse and use this law as a pretext to dispossess their Jewish neighbours, in this case the sons of Jacob.