“Now Ephron was sitting among the sons of Heth; and Ephron the Hittite answered Abraham in the hearing of the sons of Heth; even of all who went in at the gate of his city, saying, “No, my lord, hear me; I give you the field, and I give you the cave that is in it. In the presence of the sons of my people I give it to you; bury your dead.” And Abraham bowed before the people of the land.” Gen. 23:10-12
The men were gathered at the gate of the city to speak with Abraham as it was the place of official business. Ephron, who owns the cave of Machpelah which Abraham desires to buy, is present as well.
On the surface it sounds like Ephron is a great guy, but we will soon find out that is not the case. Abraham has already made a declaration that he will pay the full value of the property to Ephron if Ephron is willing to sell to him. Ephron takes this opportunity to grandstand; he tells Abraham in front of everyone “I give you the field, and I give you the cave that is in it.”
In case you didn’t catch that, Rambam points out that Ephron just changed the deal. He apparently is not interested in parting with just the cave. If Abraham wants the cave, he needs to buy the whole field with it.