Every seven years we are instructed to leave our lands fallow. This is the year of Shmittoh when the people take a sabbatical from working the soil. After seven Shmittohs i.e. after forty-nine years, we are commanded once again to refrain from farming the land. This is known as Yovel or Jubilee year. Additionally in the Yovel year all land which had been sold since the last Jubilee is now returned to its original owner. Another novelty of this year is that all Jewish slaves are set free.
Why do we have both a Yovel and a Shmittoh year? True Yovel has a new dimension in freeing slaves and terminating all leased land, but why should the soil remain barren for another year? What does the Jubilee rest accomplish over and above that of the frequently occurring Sabbatical?
Taking a look at another area of Halachah where we see a similar year differential, will help shed light on this question. We find in the contexts of the Mezuzah mitzvah a similar set of seven and fifty. The Mezuzah stands outside exposed to the elements and over long periods of time it is likely to be affected by sun, rain and humidity. Ink has a limited serviceable life and in due course the letters will fade or become erased. A Mezuzah that is missing even one letter is rendered invalid. At what point does a person have to be concerned that perhaps his doorpost no longer supports a kosher Mezuzah? The Talmud provides us with a definitive guideline:
The mezuzah of an individual requires examining twice in seven years. The mezuzah of the community requires examining twice n fifty years. (Yoma 11a)
From this law we can extrapolate a non-Halachic inference and herein we have the key to our answer; public versus private. The mezuzah inspection which scans for cracks, omissions and defects has one scale for the personal home and another for the municipal building.
Everyone needs to take stock of themselves regularly. Mesillas Yeshorim recommends that this monitoring take place daily, comparing it to inspecting scales for weighing gold. However sometimes changes and drifts develop undetected because the incremental difference is too minute to be observed. A long range diagnosis can often give interesting differing results. For example answering “how am I different from seven years ago?” or “how would I like to look in seven years from now?” is very different from answering “how am I different from yesterday?” and “how would I like to look tomorrow?”.
The same is true for the community. A similar comprehensive observance of many years may yield hitherto unnoticed transformations. The Torah commands us to abstain from working the field every seven years. A year free from work presented the people with the opportunity to take an internal scrutinization of themselves. Looking back over seven years they could observe how they had progressed or digressed. A similar prospect was engineered for the community; however changes in society take decades to develop and a larger time frame is necessary. Therefore every fifty years the Torah provided an additional year off work so that as a group they too could chart their growth and development.