The Sfas Emes writes, "According to the degree that he believes he’s leaving Egypt, so will it be."
One of the many blessings that we receive by celebrating the Seder is parnassah. The entire yom tov Pesach is conducive for parnassah, as the Gemara (Rosh Hashanah 16) states, “On Pesach there is a judgment for grain [how well the grain crops will grow].” Grain (in Tanach and in chazal) often signifies livelihood. Thus, the Gemara is saying that one's parnassah is determined on Pesach. (Especially on Shevi'i shel Pesach, as will be discussed in an upcoming section).
Rebbe Yosef Yitzchok of Lubavitch zy’a said, people in our generation think that all that they lack is for Moshiach to come. But in Egypt, they understood that waiting for Moshiach isn't enough. You have to pray for it too, like in Egypt, the salvation occurred when they shouted out to Hashem.
The Beis Aharon zt'l (p.93:) writes, "The six days [of Pesach] are a preparation for the seventh day, for the primary day is the seventh day of Pesach, since that is perfection, the day they said shirah."
Rebbe Mendel of Riminov zt’l said, "I heard from a gadol, a student of Rebbe Elimelech of Lizensk zy’a, who repeated in the name of his Rebbe that the time most conducive for attaining emunah is the night of Shevi'i shel Pesach. On this night, one should also increase his emunas tzaddikim, as that will help him attain perfect belief in Hashem. As it says ויאמינו בה' ובמשה עבדו, through believing in tzaddikim one is able to believe in Hashem."
On this day, Klal Yisrael said the shirah, Oz Yashir…. a song of praise to Hashem for the miracles that occurred. A song has high notes and low notes; some parts are sung quietly, other sections are sung out loud. This reminds us to sing when times are good, and also when times are rough; sing with the ups and the downs of life, because even the hardships are for our benefit.
The Chidushei HaRim zt'l compares Shevi'i shel Pesach to the future world, since there aren't any special mitzvos for Shevi'i shel Pesach (aside from keeping yom tov) and this resembles the future world, as chazal (Niddah 61:) state, "the mitzvos will cease in the future."
The Tzemech Tzedek zt'l said: Shvi'i shel Pesach is the Rosh Hashanah for mesirus nefesh. On this day, Nachshon ben Aminadov jumped into the Yam Suf. The water reached his nose and he shouted "Save me because the water is smothering my soul," and then the sea split. It is written, "The Sea saw and fled." The Midrash asks, "What did the Yam Suf see? It saw the coffin of Yosef." When the sea saw Yosef's bones, the person who ran away from sin with mesirus nefesh, they ran away from him and split. This is another reference to mesirus nefesh associated with Shevi’i shel Pesach.
The Reishis Chachmah (Shaar Ahavah 8:6) teaches, the lesson of the Splitting of the Sea, is to have mesirus nefesh for Hashem, and then miracles will happen.
Rebbe Michel of Zlotchev zy’a explained, when a person serves Hashem beyond his natural limits, Hashem will act in kind and perform miracles for him beyond the rules of nature.
Chazal tell us that shidduchim and parnassah are compared to kriyas Yam Suf. Therefore, the Ateres Tzvi writes, "When the sea split, it opened salvations for all generations – for the individual and for the community. Even if the gates of parnassah or the gates of shidduchim are chas veshalom closed, one should pray at this special eis ratzon by kriyas Yam Suf… and Hashem will save Bnei Yisrael when they shout out to Him."
Every miracle serves a purpose, therefore, the Sar Shalom of Belz zt'l asks, what was the purpose that all waters of the world split? He answers that water represents troubles, as it states "Save me Hashem because water (troubles) are covering over my soul" (Tehillim 69:2). The Torah tells us that "water" split, and this means it wasn’t only the sea that split; we were saved from all troubles. Throughout all generations, kriyas Yam Suf occurs again, and each year we get salvations. In particular, a person can have a salvation for those matters that are directly compared to kriyas Yam Suf, such as parnassah and shidduchim
The Bnei Yissaschar (Chodesh Nisan 13:2) states, "I heard from my holy mechutan, Rebbe Hershel of Ziditchov zt'l that… the Torah specifically writes [the permission to prepare food] on Shevi'I shel Pesach to teach us that on this day… it’s easier, keviyachol, for Hashem to bestow good parnassah to the Jewish people, even if they don’t have sufficient merits, chas veshalom."
The Beis Avraham zt'l would tell those who needed a shidduch, parnassah, or a refuah to say the entire Tehillim on Shevi'i shel Pesach, because it’s a day of salvations.
The month ניסן (from the word נס) implies that it’s a month when miracles occur. The Rebbe of Ruzhin added that ניסן, with a 'ן' at the end, implies that miracles happen constantly this month, since the 'ן' at the end of a word represents something that happens often. As chazal (Bava Metzia 33.) say that when the passuk discusses a donkey that buckles under his load and people are obligated to help the donkey get up, it states רובץ, "crouched down." It doesn’t state רבצן, because that would imply that it sits down very often, and if that is the animal’s nature, you aren't obligated to help the animal get up. We see from this Gemara that a 'ן' at the end of the word implies to something that happens often. Similarly, many occupations have a 'ן' at the end of the word. For example, רצען is a shoemaker, קבלן is a contractor, and so on. The extra 'ן' implies that this is their occupation, something they are always doing. Likewise, ניסן means that miracles are always happening in this month.