The first pilgrimage feasts begin with Pesach (seven days in the Land of Israel beginning on 15 Nisan), Pesach is the oldest festival in the history of Israel, commemorating the liberation of the Israelite slaves from Egypt and with it the birth of the Hebrew nation.
The name "Pesach" comes from the Hebrew root Peh-Samech-Chet, meaning to pass through, to pass over, to exempt or to spare. It refers to the fact that God "passed over" the houses of the Jews when he was slaying the firstborn of Egypt (Exodus 12:27). "Pesach" is also the name of the sacrificial offering (a lamb) that was made in the Temple on this holiday (Exodus 12:3-20).
There are a few names for this festival:
Chag Ha'aviv (The Spring Festival) – Pesach must take place in the spring,
when nature comes to life again after the dark winter. A period of rebirth that matches the birth of the Jewish nation. This holiday marks and
celebrates the harvest of the early barley.
Chag Hamatzot (Festival of the Matzot) – "Seven days shall ye eat unleavened bread; howbeit the first day ye shall put away leaven out of your houses; for whosoever eateth leavened bread from the first day until the seventh day, that soul shall be cut off from Israel" (Exodus 12:15). This recalls the hasty Exodus from Egypt when the Israelites had time to prepare only unleavened bread.
Zeman Cheiruteinu (Season of our Freedom) – The festival is so described because it marks the liberation of Israel from Egyptian bondage and its birth as a free nation.
The first Seder is after the 14th of Nisan.
On the first night of Pesach there is a special family meal filled with ritual to remind the Jew of the significance of the holiday. This meal is called the Seder from a Hebrew root word meaning "order", because there is a specific set of information that must be discussed in a specific order. The text of the Pesach Seder is written in a book called the Haggadah - "Narrative".
The Haggadah tells the story of the Exodus from Egypt and explains some of the practices and symbols of the holiday. Its history goes back to the early Talmud period, c.100 CE. From an educational perspective, the Haggadah has been arranged to keep the children's interest. Children ask why this night is different from every other, and the parents respond with answers.
From generation to generation each tells the story as if they themselves personally came out of Egypt. The Seder service is divided into some fifteen sections, each indicated by a descriptive name. The purpose of the Seder is to symbolize important features and lessons of the Exodus and the redemption. On that night Jews start counting the omer. The counting of the omer is a counting down of the days from the time they left Egypt until the time they arrived at Mount Sinai. No leavened food is eaten during the week of Pesach.
Christians refer to Jesus final Pesach with His disciples as the “Last Supper” (Matt. 26:20-30).
Pesach lasts for seven days (eight days outside of Israel). The first and last days of the holiday (first two and last two outside of Israel) are days on which no work is permitted.
The Passover is completed with the phrase: Lashanah Haba'ah Bi Yerushalayim! - Next Year in Jerusalem!