Chasidut su Levitico 23:15

Leviticus 23,15. “you shall count for yourselves from ‎the day following the festival, (Passover) etc.;” we need to ‎understand first of all why the festival of Passover is referred to as ‎‎Hashabbat in our verse. This has been explained by our ‎sages, (Tanna de bey Eliyahu 14) where the author interprets ‎the word ‎בראשית‎ as meaning ‎בשביל ישראל‎, “for the sake of Israel.” ‎Granted that this is true, it did however, not come to the ‎attention of the world until G’d redeemed Israel from Egypt when ‎His love for His people manifested itself. As a result, Passover ‎became similar to the Sabbath. The Sabbath is unique as on the ‎Sabbath G’d abstained from His creative activity, whereas, ‎according to the Zohar, on Passover He abstained from ‎entertaining thoughts. When G’d “rested” on the original Sabbath ‎His work during the preceding six days was revealed for the first ‎time. Similarly, His love for the Jewish people was revealed for the ‎first time on the occasion of the redemption from Egypt, i.e. the ‎day of the Exodus. On the first day of Passover it finally became ‎clear why G’d had bothered to create the universe altogether. In ‎other words, Passover may be looked upon as the logical ‎conclusion of what had been set in motion the moment G’d had ‎first thought of the people of Israel as a project for the future. ‎This is also the meaning of a statement of the sages in Shabbat ‎‎118 that if the Israelites were to observe two Sabbath days, i.e. ‎the terrestrial Sabbath as well as the celestial Sabbath, they would ‎be redeemed immediately. The scholar to whom this statement is ‎attributed quoted Isaiah 56,4 in support, where G’d promises ‎redemption to the eunuchs who keep His Sabbaths, following up ‎in verse 7 with: “and I will bring them to the Mountain of My ‎holiness etc,. etc.” The “two” Sabbaths of which the Talmud ‎speaks are not to be understood quantitatively, i.e. 2 separate ‎Sabbath days, but refer to the ‎שבת תחתון‎ and the ‎שבט עליון‎, ‎observance of the Sabbath with our body, i.e. ‎תחתון‎, and at the ‎same time observing it with our hearts and minds, i.e. ‎שבת עליון‎, ‎the Sabbath in our upper regions, our heads. The more the ‎Israelites engage in serving the Lord, the clearer it will become ‎that G’d only created the universe on account of the Israelites. ‎There is an allusion to this in the letters of the words ‎מן פסח‎ ‎when we reverse the order of the aleph bet, i.e. that the ‎letter ‎א=ת, ב-ש, ג=ר‎ etc. [Magen Avraham on the laws ‎of the New Moon chapter 428, subsection 3 deals with this in ‎greater detail, i.e. that certain festivals must occur on the ‎weekdays corresponding to other festivals preceding them during ‎the same year. Ed.] ...

And this is the aspect of Shabbat HaGadol, which is the name of the Shabbat before Passover, on account of the miracle, etc. The essence of the miracles and wonders that took place during the Exodus from Egypt - which crumbled the battles and nullified nature and revealed His Blessed Providence to the world - all of it was drawn from the aspect of Shabbat, which is the Future World which is totally Shabbat. From there, Hashem Yisbarach drew, so to speak, divine providence from the ends of the earth, etc., corresponding to (Ezekiel 7:2) "an end! The end has come", etc., as is brought there in the lesson as seen above. The essence of the Exodus from Egypt is drawn from Shabbat, which is the aspect of the World to Come. Therefore, Pesach is also called Shabbat, as it is written (Leviticus 23:15) "And you shall count for yourselves, from the morrow of the rest day"; in other words, Pesach, which our Sages of Blessed Memory said (Menachos 65b) that the essence of the power of the miracle of Passover is drawn from Shabbat, as explained above. This is the aspect of the Shabbat that is before Passover, which is called Shabbat HaGadol because of the miracle. For all of the miracles of the Exodus from Egypt were drawn from the aspect of Shabbat, as explained above. Therefore it is called "Gadol" because of the miracles which were called the aspect of Gadol (great), as it is written (II Kings 8:4) "Please tell me all the great things that Elisha performed". As Rabbeinu z"l wrote there in the lesson as seen above, 'And 2 tears went down into the great sea', see there.

While the Israelites were in Egypt they had not ‎attained more than the first virtue (attribute) i.e. ‎אמונה‎, ‎‎“faith,” as the Torah testifies in Exodus 4,31‎ויאמן העם‎, ‎‎“The people possessed faith.”‎
We have already explained that the feet (legs) ‎symbolize faith and that is why at the Exodus, (12,37) ‎the Torah describes the Jewish people leaving Egypt by ‎referring to them as ‎כשש מאות אלף רגלי‎, “approximately ‎‎600,000 pairs of feet.” The other virtues that the ‎Israelites did not yet possess at the time of the Exodus, ‎they would acquire at the “foot” of Mount Sinai, seven ‎weeks later, at the time when G’d gave them the Torah. ‎This progress of the Israelites’ spiritual development is ‎hinted at in the details with which the Torah describes ‎the Passover offering. The sequence of the words: ‎ראשו ‏על כרעיו ועל קרבו‎, suggests that at that time the virtues ‎other than faith, ‎כרעיו‎, were still as hidden as are the ‎entrails. When we keep this in mind, we can ‎understand a statement in the Talmud ‎‎Menachot 65, where the verse ‎וספרתם לכם ממחרת ‏השבת‎, ”you shall count for yourselves starting from the ‎day after the Sabbath,” is understood to refer to the ‎day after the first day of the Passover festival. This ‎contradicts the interpretation of the Sadducees who ‎understood the word ‎השבת‎ in that verse as referring ‎literally to the first Sabbath day during that festival.