On Passover one is prohibited to possess Chametz (leaven). All Chametz that will not be eaten or burned before Passover must be sold to a non-Jew. Any Chametz remaining in the possession of a Jew during Passover may not be used, eaten, bought or sold even after Passover.
Therefore, all Chametz and Chametz utensils must be stored away. The storage area should be locked or taped shut to be leased to the non-Jew at the time of the Chametz sale.
There are many legal intricacies in this sale; thus only a Rabbi should be entrusted with its execution. The Rabbi acts as our agent both to sell the Chametz to the non-Jew on the morning before Passover starts and also to buy it back the evening after Passover ends.
Locking your Chametz away and sending your signed Chametz Contract to Rabbi Slonim is an easy way of observing this.
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