Jeremiah 32:10

So Abraham heard Ephron; and Abraham weighed out for Ephron the silver which he had named in the hearing of the sons of Heth, four hundred shekels of silver, commercial standard.

So the field and the cave that is in it were deeded over to Abraham for a possession for a burial site by the sons of Heth.

‘Men will buy fields for money, sign and seal deeds, and call in witnesses in the land of Benjamin, in the surroundings of Jerusalem, in the cities of Judah, in the cities of the hill country, in the cities of the Shephelah, and in the cities of the Negev; for I will return their fortunes,’ declares Yahweh.”