It is a person's responsibility to acknowledge that having done nothing to deserve it H'shem raised him, as a gift and a favor.
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21 The Biur Deadline III
We learned that at the end of a food’s growing season, someone who still has some of this food must perform the mitzvah of biur, ridding, by rendering it hefker.
Each type of food has its own biur deadline. Several of them are clearly enumerated in the Gemara; the biur deadline for dried figs is Chanukah, for dates is Purim, for grapes is Pesach, and for olives is Shavuos, all in the year following Shemittah. The biur dates for other types of foods depends on the specifics of the growing season. Kashrus organizations in Eretz Yisrael publicize detailed charts with the specific biur times for each type of produce.
The Biur Deadline IV
Shemittah food for which biur was not performed may not be eaten, and must be destroyed. (This halachah is often relevant with processed foods and drink with a long shelf life, such as Israeli bottles of wine, and canned goods, that are stored and marketed after the biur deadline.)
A halachic authority should be consulted regarding foods upon which biur was not performed accidentally, or inadvertently, such as if the person who owned the foods was unaware that the biur deadline passed.