“that he owns.” Abraham, an astute businessman, is making sure that Ephron does indeed own the field and thus has the right to sell it. It is amazing how many real estate transactions occur and the buyer later finds out that the person who “sold” the land did not have clear title. Anyone buying or selling land can learn things from Abraham.
“which is at the end of his field.” Abraham is making it clear that he does not want to buy all of Ephron’s land, only the cave.
“full price.” The Hebrew is “full silver,” and reflects the custom of trading using precious metals by weight. Coins had not been invented yet. Abraham is also making sure the Hittites know he is buying the land as a permanent possession, he is not just using the cave to bury Sarah.
“property.” God had promised Abraham the land, and so he knew that someday it would be his and his descendants, but how that would happen had not yet been revealed. Nevertheless, Abraham takes a stake in the Promised Land by buying a burial site for his property. See commentary on Genesis 23:4.