The 117th mitzvah is that we are commanded regarding the financial evaluation (erachin) of fields.

The sources for this commandment are G‑d's statements,1 "If [a person consecrates] a field from his hereditary property..." and "If the field is not his hereditary property but a field he has bought...."

If it is hereditary property, "its value shall be calculated according to the amount of seed [required to sow it]."2

If the field was purchased, "The kohen shall calculate the proportion of its value [on the basis of the number of years remaining until the jubilee year]."

The details of this mitzvah are also explained in tractate Erachin.

Do not think that these four categories of evaluation share something in common which requires them to be counted together as one mitzvah. Each one has its unique regulations, and is therefore counted separately. All they share in common is the title "evaluation" (erach). Therefore, the various categories of erachin cannot be counted as only one mitzvah just as the various types of sacrifices are not counted as only one mitzvah. After careful consideration, this will become clear.