Thus if a sukkah made last year still has its s’chach, its roof-covering of greenery, intact and usable, it sounds wonderful but it is not a kosher sukkah.
Only if one makes the effort to replace or at least re-arrange the s’chach will it be kosher. One must inject personal effort into the mitzvah.
There is a wider significance, a higher symbolism in this law.
Like last year’s s’chach, the Jewish heritage is something derived from the past, an inheritance from our ancestors.
It is good to be proud of the past, but that can never be enough. Jewish survival depends on ta’aseh v’lo min he’asuy, on personally involving oneself in Jewish life and strengthening and enhancing the tradition.
Remain content with memories of the past, and you imperil everything. Ta’aseh, live as a Jew, making your own effort, and Sukkot will be chag same’ach and Judaism ach same’ach, safe, joyful and forward-looking.