If a slain person be found in the land that G-d, your
G-d, is giving you to possess, lying in the field, and
it is not known who slew him.
Deuteronomy. 21:1
The purpose of the ritual the Torah prescribes in order to atone for an unwitnessed, unsolved murder is to publicize it, so that it will be easier to locate the murderer, and – more to the point – so that everyone be made aware that the murder occurred. This way, the people will be inspired to do whatever they can to ensure that such a horror not occur again.
Allegorically, the “field” in which the victim is found is an area outside of a settled, civilized city or town – i.e., a realm devoid of spiritual consciousness. Those who are found in this realm are vulnerable to the forces of blind materialism that seek to “murder” them, i.e., to sap the spiritual life from them, leaving them deadened to Divinity.
The Torah therefore teaches us that it is our responsibility to ensure that such a calamity never occur. We do this by embracing and welcoming our “stranded” brethren into our midst, and by spreading Divine consciousness everywhere, transforming even the most deserted “field” into G-d’s true home.
--Daily Wisdom Volume 3