Or HaChaim on Genesis 23:11/אור החיים על בראשית כ״ג:י״א

1 לא אדוני, "No my lord." The word "no" means that Abraham could not merely acquire the cave but had to buy the field it was situated on. Efron indicated that the reason he had decided to give the whole field to Abraham was that once it served as a cemetry it could not longer serve its original purpose. He implied all this by using the word שמעני, "listen to me carefully."

2והמערה אשר בו, "as well as the cave situated on it." He meant that already at the very beginning of the discussions when the local people had indicated their willingness to relinquish their own burial plots in favour of Abraham, he, Efron had decided that the cave and the field were a single unit. The reason he repeated the fact that the transaction took place in full view of all the people was to make plain that no דין מצר could be invoked by anyone in the future.