The seventh day of Passover is the conclusion of Passover. As with all Jewish holidays, the holiday begins the evening before the day of the holiday and ends on the evening of the day of the holiday itself.
This day of Passover marks the day when many miracles were performed for our forefathers at the Red Sea. The Torah (in Exodus, 12:16) states, ”…and the seventh day shall be declared a holy day for you. No work shall be done on that day.”
This holiday commemorates the day the Children of Israel reached the Red Sea and witnessed both the miraculous "Splitting of the Sea," the drowning of all the Egyptian chariots, horses and soldiers that pursued them, and the Passage of the Red Sea.
The seventh day is another full Jewish holiday, with special prayer services and festive meals. Outside of the Land of Israel, the seventh day of Passover is celebrated on both the seventh and eighth days of Passover.
The essence of the celebration of this day is the song that Moses and Israel were divinely inspired to sing on this day, a song that merited being included in the Torah, a song to which God and His heavenly hosts listened. The Song of Moses and Israel can be found in the book of Exodus 15:1-18.