The Gemara in Kiddushin derives the halachic model of marriage from the transaction that took place between Avraham and Efron for the Mearas HaMachpela.
When students learn this, it is easy to misconstrue. How is getting married anything like buying a field?
Rav Shamshon Raphael Hirsch explains that the analogy of the transaction takes place in a much wider context.
The land of Israel is indelibly woven into Jewish history and identity for eternity. This interaction was the first act, by the first Jew, on the land of Israel. The Mearas HaMachpela, and what Avraham went through to get it, is the first link in the eternal bond between the land of Israel and the Jewish people.
The Mearas HaMachpela was a double storeyed structure, and special in that it’s structure enabled our ancestors to be buried together privately as couples. Husband and wife, parent and child, remained together. The first act on the land of Israel was to secure the future of family ties.
The analogy to marriage makes far more sense in this context because it transcends a simple land transaction. The land is God’s eternal commitment to us, and marriage is our eternal commitment to each other.