Genesis 23 describes Avraham's purchase of a burial site from Efron the Hittite. The way Haamek Davar explains it — if I understand his commentary to verse 20 correctly — the transaction that was made (verses 17–18) did not include any mention of what the site would be used for. Yes, that use had been mentioned in the preliminary discussion (verses 4–15), but it was not a condition of the actual transfer of ownership. Only by burying Sara (verse 19) did the land become established as Avraham's burial site (verse 20) and did the neighbors lose their right to protest such use of the land. (A burial site increases foot traffic. [Apparently, according to Haamek Davar, this was not known to be a burial site hitherto.])
Why didn't Avraham make the land use a stipulation of the transaction itself? That would immediately prevent anyone from protesting such use! And it's not like it was a secret: the whole town knew he was out to buy a burial site.