Chasidut for Shabbat 236:2

Exodus 16,25. “eat it this day for this day is the ‎Sabbath for G’d; this day you will not find any of it in the ‎field.” With these words we can answer the question raised ‎by Rabbi Moshe Alshich why the manna did not descend on the ‎Sabbath, whereas G’d did not interfere with the continued ‎growing and developing of crops that originate in the earth. The ‎fact that the manna did not descend on the Sabbath is a reminder ‎that whereas normal crops originate from indirect largesse of G’d, ‎i.e. His largesse making a detour via the bowels of the earth and ‎requiring the “help” of rainfall, and the many steps a farmer must ‎invest before he finally has a loaf of bread to show for his toil. The ‎Sabbath is a symbol of G’d’s direct largesse, the ready made ‎‎“bread” having been sent to earth already on the eve of the ‎Sabbath, so that the spiritual dimension of the Sabbath does not ‎need to be diminished, desecrated. This concept has been alluded ‎to in the Talmud Shabbat 118 where we are told: ‎כל‎ ‎המענג ‏את השבת נותנים לו משאלות לבו‎, “whoever will gladden the Sabbath ‎will have his heart’s desires fulfilled.” The scholar making that ‎statement supports it with a verse from psalms 37,4 ‎והתענג על ה' ‏ויתן לך משאלות לבך‎, “endeavour to provide pleasure for the Lord, ‎and He will grant you the desires of your heart.” Apparently, ‎according to the Talmud, the principal enjoyment G’d derives ‎from the Sabbath is the very existence of that day as such. Rav ‎Yehudah, the author of the above quoted statement, considers ‎the principal pleasure to be derived from the Sabbath not the ‎additional food and drink and its superior quality, but the ‎appreciation that G’d created such a day, a day that enables us to ‎reflect on the fact that the purpose of our existence is not ‎exhausted by our being able to provide for our material needs, ‎but to enable us to intensify our link to the celestial domain in ‎which the Creator resides. When the sages composed the central ‎prayer of the Sabbath service that commences with the words: ‎תכנת שבת‎, “You have established the Sabbath, etc,” they arranged ‎for the words to commence with the letters of the alphabet ‎beginning with the last letter and concluding with the first letter. ‎In other words, the message of the Sabbath is to take us back ‎from a material world to the totally spiritual world that existed ‎before G’d commenced with creating the light. We have dwelled ‎on the idea that a human being who is spiritually successful will ‎‎“bounce back” the light that G’d created and used to illuminate ‎the physical universe. Our author, at that time, described this ‎‎“bouncing back” of “light rays” to G’d by human beings as the ‎highest accolade we are capable of, as it proves that His light ‎inspired us spiritually. At that time our author explained that the ‎light created on the first day of creation is perceived as ‎אור ישר‎, ‎‎“direct light,” whereas the “light” bounced back by us is ‎perceived as ‎אור חוזר‎, “reflected light.” The sages’ arrangement of ‎the prayer ‎תכנת שבת‎, reflects all this. Once we appreciate this we ‎understand why it was natural for no manna to descend to earth ‎on the Sabbath. The very descent of manna from heaven is an ‎example of “direct light,” i.e. largesse descending from heaven to ‎the material world directly, whereas the Sabbath is reserved for ‎grateful man to “kick back” some of that light after he has ‎‎“garbed” it with spiritual input of his own.
The reason why normal crops continue to grow without ‎interruption on the Sabbath is because the whole universe has ‎been created for the benefit of the Jewish people, and all the ‎crops that grow are meant to serve the needs of the Jewish ‎people, first and foremost. When the Jew eats and drinks, ‎partaking of G’d’s largesse, he does not do so in order to indulge ‎himself but in order to help him to better serve his Creator. The ‎ripe crops therefore can be viewed as a microcosm of the concept ‎of the Sabbath, i.e. they serve to refine the human being and to ‎help him become the ideal man G’d had envisioned when He set ‎out to create him. Ingestion of the food grown by the earth by ‎Torah observant Israelites, not only enhances the spiritual ‎development of the Israelite consuming it, but converts the food ‎itself into part of the spiritually advancing Israelite himself. The ‎very process of the crops growing even on the Sabbath are only a ‎stage in this “kickback” by the Israelite, or ideal man, of the now ‎spiritually enhanced light that originally came forth when G’d ‎created ‎אור ישר‎, “direct light.”
The phenomenon of the ‎splitting of the sea may be understood in a similar manner. When ‎the ocean was first created, this was parallel to the creation of ‎light, i.e. an emanation of what had previously been something ‎spiritual, i.e. something “travelling” downwards from a higher ‎celestial domain. When the sea was split, it travelled in the ‎opposite direction, emanation in reverse. Since it did so by ‎fulfilling its Creator’s directive, it made a positive contribution, ‎just as did a human being who ingests food in order to serve his ‎Creator. This was a strictly temporary situation, so that when it ‎returned ‎לאיתנו‎, “to its original condition,” it resumed its normal ‎function. This is the mystical dimension of the three verses of 72 ‎letters each, which alternately have to be read in opposite ‎directions to enable us to read the 72-lettered name of G’d. ‎‎(14,19-21) The first verse is read from right to left, the second ‎from left to right, and the third again from right to left. The ‎three verses are written above one another. ‎‎