'Purchase' in the Bible

Adah gave birth to Jabal; he became the father of those [nomadic herdsmen] who live in tents and have cattle and raise livestock.

to Abraham by purchase, before the eyes of the sons of Heth, among all entering the gate of his city.

Are we not reckoned by him as foreigners? For he has sold us, and has also entirely consumed our purchase price.

However, he did not purchase land belonging to the priests, because the priests held an allotment, previously provided to them by Pharaoh, from which they lived. That's why they did not sell their land.

The purchase of the field and of the cave that is therein was from the children of Heth.