Doreish Tov Le'amo on Pesah Le'atid Lavo
Translated from here, from a Shabbat HaGadol Derasha by R' Shmuel Tuvia Stern of Miami Beach in 5748:
...So, since everyone must show himself as if he left Egypt, he thereby brings himself to the Pesah of Egypt - in other words, the Pesah of Egypt, the Pesah of later generations and the Pesah of the future is all one thing. This is because if we look carefully into the verses of the Torah, we find in the Parsha of Pesah 3 times in Parshat Bo. First, it says:"Speak ye unto all the congregation of Israel, saying:"..."and the whole assembly of the congregation of Israel shall kill it". Later, it says: "Then Moses called for all the elders of Israel, and said unto them: 'Draw out, and take you lambs according to your families, and kill the passover lamb.'" Later, it says: "And the LORD said unto Moses and Aaron: 'This is the ordinance of the passover'". We find, first of all, that it only says "לאמר (saying)" in the first Parasha of Pesah, which is "unto all the congregation of Israel" - that is the Pesah of the future, but it does not say לאמר for later generations - neither by the elders of Israel nor by Moshe and Aharon. We now have 3 categories of Pesah - Pesah to all the congregation of Israel, Pesah to the elders of Israel, and Pesah to Moshe and Aharon - and one can say that they represent Pesah of Egypt, Pesah for later generations, and Pesah of the future. There is an opinion that only Moshe and Aharon ate from the Pesah of Egypt originally, and only after they were circumsized and dipped did all of them eat. The reason is because Moshe and Aharon were of the redeemers - not those being redeemed - so they merited to eat the Pesah before the time of redemption since the redemption was only done at midnight and the Korban Pesah was eaten before midnight. The Pesah of later generations was to the elders - in other words, it was given over to the Sanhedrin, who are the elders, and they make leap-years and sanctify the new moon, so Pesah can only be celebrated through them. But in the future, Pesah will be for the entire congregation of Israel and that is why it is written in this Perasha to show us that in the future, there will not be anyone uncircumsized or unclean or on the road because in the future, Yerushalayim will spread throughout the Land of Israel, as we say "ולירושלים בית מקדשך (and to Yerushalayim, Your Beit Hamikdash)". In other words, all of Yerushalayim will have the aspect of the Beit Hamikdash and all of the Land of Israel will have the aspect of Yerushalayim and the entire world will have the aspect of the Land of Israel.
And it is not for nought that our enemies want us to revert and return areas from the Land of Israel which were sanctified with the sanctity of Ezra, which is never cancelled and is sanctified forever. And if we Has VeShalom do revert, we are denying the future to come. Any return from the Land of Israel, which was captured with "Damim Yekarim" ("Damim" - with the singular connotation of the blood of our bretheren, the children of Israel), contains, Heaven should save us, a lacking in the complete Emuna of the future to come soon in our days, and with this, we delay and prevent the Redemption. This is because instead of expanding the Land of Israel, we are contracting the borders of the Land in the returning of territories. This goes against the prophecy that Yeshayahu prophesied: "Enlarge the place of thy tent, and let them stretch forth the curtains of thy habitations, spare not; lengthen thy cords, and strengthen thy stakes. For thou shalt spread abroad on the right hand and on the left; and thy seed shall possess the nations, and make the desolate cities to be inhabited."
And in the future to come, HKB"H will gather the dispersed of Israel through Mashiah Tzidkeinu, and will not leave over anyone in exile. Therefore, there will be a complete Redemption with the completeness of redemption, completeness of the nation, completeness of the Torah, and completeness of the holy land. One can find a hint to the 4 "completenesses" in the 4 expressions of redemption in the hint of תרי"ג, which is an acronym of תשובה Teshuva - complete repentance, רפואה healing - complete healing, ישראל Israel - complete Land of Israel, and גאולה redemption - complete redemption. And all is through the holy Torah and the תרי"ג or 613 Mitzvot. And these correspond to the 4 expressions of redemption: ת hints at תורה, which corresponds to ולקחתי, as it says "כי לקח טוב נתתי לכם תורתי אל תעזבו". The letter ר hints at רפואה, which corresponds to והצלתי, which is separating between death and life, as it says "ואת בתינו הציל". The letter י hints at ישראל, which corresponds to והוצאתי, as it says "והוצאתי את עמי ישראל". The letter ג hints at גאולה, which corresponds to the Land of Israel, as it says "גאולה תתנו לארץ". These are 4 complete cups since every cup needs to be complete - the completeness of the cups hint to the completeness of the redemption because in the Pesah of the future, we will merit an eternal freedom, and we will soon in our days hear the Shofar of Mashiah when our prayers will be fulfilled when we say, "תקע בשופר גדול לחירותנו"...