Our Gemara on Amud Aleph quotes the verse that describes the Biblically mandated process of redeeming a field that one declared hekdesh (consecrating it for the Temple treasury). It is redeemed according to a standardized scale of fifty shekels of silver per an area fit to sow a ḥomer of barley.

Mei HaShiloach (Volume II, Leviticus, Bechukosai) wonders about the purpose of this process. Why would the Torah enshrine a process of the owner redeeming the field?  If the Torah described the process of a public auction as the primary way to cash in the field, this would make sense as the owner donates the field, while the treasury could shrewdly sell it for more. This is like people who donate stocks or cars to charities which then sell them off at a profit. But why should the person go back on his declaration? And if the original donor wanted to fund hekdesh and he had the cash on hand, why not donate it directly?  Mei HaShiloach suggests that this action is performed by someone who has wealth and assets, but feels he is becoming seduced by the trappings and demands of materialism.  He declares the field hekdesh, even though he plans to buy it right back, as he needs this property. This is done solely to break his attachment to the material and remind himself that it really comes from God.

Another peshat could be similar to what Tur HaAruch (Vayikra 14:34) says is the reason some Jewish homes were afflicted with blemishes that required cutting out parts of it, or even total demolition (VaYikra, chapter 14): Some of the homes had left over residue of impurity from the prior idolatrous owners. They were so toxic that they could not be countered or overcome without complete excision.  So too, perhaps a person might feel his field to be cursed with bad mazal. By making it the possession of hekdesh, and then buying it back, this would allow it to be cleansed and start fresh.

Each of these reasons cover a different kind of corruption and contamination. The first one of arrogance is an internal state and association to the field that must be reset, and the second one is an external impurity that must be removed. Regardless of which explanation we go with, and both can be true, we see that sometimes purification or turning over a new leaf requires a physical act or change of status in order to concretize the resolve. This is one of the inescapable aspects of psychology and spirituality, symbolic physical acts motivate and activate.  As we dip the apple in the honey, or throw our sins in the water, we can understand this as prayer via action. The Gemara (Kerisus 6a), declares: Symbolic actions are significant and thus one should eat various foods that serve as good omens for the new year.