In preparation for the tenth plague, Hashem tells Moshe and Aharon (12:13), “Vehayah Hadam Lachem Leot Al Habatim Asher Atem Sham, Vera’iti Et Hadam Ufasachti Aleichem, Velo Yihiyeh Vachem Negef Lemashchit,” “The blood should be a sign for you upon the houses where you are, and I will see the blood, and I will skip over you, and there will not be among you a plague to destroy.” We can see that the purpose of the blood (at least on the surface) was to serve as a sign indicating a Jewish house. If so, why did the Pasuk say that the blood would be Lachem, “for you,” rather than Li, “for me?” Why did the Jewish people need a sign if it was really for Hashem?
Sefer Chagai states (2:9), “Gadol Yiheyeh Kevod Habayit Hazeh Haacharon Min Harishon.” The Rabbis learn from this (Bava Batra 3a) that the second temple would be larger and last longer than the first temple.
The Rashba was once asked by a non-Jew how he could possibly believe that there will be a third temple rebuilt and Mashiach will come if the prophet referred to the second temple as Haacharon, “the last.” The Rashba responded that one can interpret Haacharon to mean “second” in this context, as the word Haacharon does not always mean last. This can be proven from Hashem's three signs given to Moshe to prove his authenticity as the redeemer of Bnei Yisrael. The Torah writes the first sign was the staff becoming a snake. The second was Moshe's hand becoming leprous. Hashem tells Moshe that if the first sign is not good enough, the people will listen to “Ha’ot Haacharon,” the last sign (4:8) and believe that Moshe was sent by G‑d. Why did He refer to the second sign as “Ha’ot Haacharon” if there was a third sign? The obvious answer is that Haacharon does not always mean last, but also can mean second.
Hashem told Bnei Yisrael through Moshe that the third sign would be “Lachem Le’ot,” “for you a sign,” a sign that the third Beit Hamikdash will be built in the future. Hashem is going to gather us from the four corners of the earth as we say in the Beracha of “Teka Beshofar Gadol” in the Shemoneh Esrei. Hashem will reunite us in Israel for the creation of the third and final temple. This may seem hard to comprehend because of the current conflict in Eretz Yisrael over the Gaza situation, where (in a worst-case scenario) a civil war could break out, but we must have Emunah (hope) in Hashem that He will keep His promise that one day we will all be united as one Jewish nation living in Eretz Yisrael.