Buying land - Dira Be'Tachtoinim

The Rambam in the Laws of Selling, 81,  explains the ways of acquisition – “ How does one make a purchase? In the case of a land acquisition, it’s in one of three ways: with money, with a document, or by possessing it.” This idea of “selling” in terms of one’s service of G-d is the removal of the mundane in this world and transforming it into a mitzvah or holiness – Dira be’Tachtoinim. And this relates to the three ways of acquisition: they correspond to the three lines of Torah, avoda, and kind deeds. The right, left, and middle directions or chesed, gvurah, and tiferes (kindness, severity, and splendor). These concepts are applicable to the acquisition of Eretz Yisroel to Hashem and parallel  the ways of acquiring a wife: money, a document, relations. (The “property” here is the external element, whereas the kuddishin and acquisition are internal.)

And when it comes to avoida – the beginning of true avoida is in an external way and later, internally.

And continues Maimonides "he who sold a home, also sells the buyer  the  field or the fence, etc.  because it benefits the transaction”. That means that the idea of an acquisition to Hashem  in the world, i.e. transforming the materiality, has to have a benefit which needs to bring about a novelty in the world. 

Based on a sicha from
יום ג' פ' ויצא, ו' כסלו, ה'תשע"ג