The Shabbat that comes before Passover is called Shabbat HaGadol. The Hebrew word gadol means “big” or “great.” So Shabbat HaGadol means, “the great Sabbath” or “the Sabbath of the great.”
Jewish thinkers have put forward many ideas about why it is called by this name. Jewish communities observe many special customs on this day as well. One common custom is to read a specific section of the Passover Haggadah in the afternoon.
It might seem that the purpose of reading the Haggadah on Shabbat HaGadol is to rehearse for the upcoming seder. But that idea raises some questions.
First, why specifically do so on Shabbat? Passover begins on a certain day of the month, not a day of the week. This means Shabbat HaGadol might be anywhere from a week before the seder to just a couple of hours beforehand. If we wanted to rehearse the seder, it would make sense to do so the day before or a certain number of days before, but there would not be a need to do so on a specific day of the week.
Second, why recite only this part? On Shabbat HaGadol we read a portion from the section called Maggid, or telling the story. It begins with the statement “We were slaves to Pharaoh in Egypt.” The section includes the story of the five rabbis, the four sons, the exposition on Deuteronomy 26, and the ten plagues. Then it concludes with Dayenu (“It would have been enough!”) and the statement that God built the Temple “to atone for all our iniquities.”
This is the easiest part of the seder. It is basically just a reading. There is no rehearsing about when to pick up the cup or put it down, when to cover or uncover the matzah, when to lean or when to sit up straight. Some of the most important and interesting parts of the seder are missing. If this were a rehearsal, wouldn’t we practice the whole ceremony?
The Abomination of Egypt
The code of Jewish law gives a different explanation for the reading. The reason it gives is “because Shabbat HaGadol was the beginning of the redemption and the miracles.” This means that the reading is not just for practice. It’s more like a brief seder itself! We are reading because the miracles of Passover began on that day. What miracles? When Moses stood before Pharaoh, and Pharaoh insisted that they could offer their sacrifices to God without leaving Egypt, Moses answered,
It would not be right to do so, for the offerings we shall sacrifice to the LORD our God are an abomination to the Egyptians. If we sacrifice offerings abominable to the Egyptians before their eyes, will they not stone us? (Exodus 8:26)
Rather than “an abomination to the Egyptians,” the Hebrew text literally says, “the abomination of the Egyptians.” According to Jewish interpretation, the Egyptians worshiped a lamb god. Sacrificing a lamb would be offensive to the Egyptians because it represented the slaughter of their false deity—their “abomination.” 
But despite the objection of Moses, the situation he described came to pass. While in Egypt, God told Moses and Aaron, “Tell all the congregation of Israel that on the tenth day of this month every man shall take a lamb according to their fathers’ houses, a lamb for a household” (Exodus 12:3).
Jewish tradition holds that in the year of the exodus from Egypt, the tenth day of the month of Nisan fell on Shabbat. The Israelites were aware that the Egyptians would be incensed by their lamb sacrifice and that they might be taking their lives into their hands, just as Moses said. Yet each of the Israelites took a lamb and tied it to the bedpost, in accordance with the command.
When the Egyptians saw the Israelites taking their lambs, they asked them why they were doing this. The Israelites bluntly answered, “To slaughter as a Passover offering as HaShem has commanded us.” The Egyptians were grinding their teeth in anguish, but they were unable to do or say anything to stop the Israelites. This was the miracle that marked the beginning of redemption.
Freedom from Fear
Shabbat HaGadol represents the idea that God is greater than what we fear. He is greater than the power of others to bully or intimidate us, to prevent us from carrying out his will. Among the many psalms in the Passover seder, we read this verse of praise:
The LORD is on my side; I will not fear. What can man do to me? (Psalm 118:6)
The first step of freedom and redemption from our slavery begins with freedom from fear. What will the neighbors think if I don’t act like them? What will people say if I live a strange life as a follower of God’s commandments? Freedom means we don’t let those questions stop us. As Shimon taught,
Now who is there to harm you if you are zealous for what is good? But even if you should suffer for righteousness’ sake, you will be blessed. Have no fear of them, nor be troubled, but in your hearts honor Christ the Lord as holy, always being prepared to make a defense to anyone who asks you for a reason for the hope that is in you. (1 Peter 3:13-15)
Standing out in obedience to God may not keep us from persecution, but in the end, it is worth every bit of it. Step out in faith this year, and may we see the ultimate redemption take place soon with the return of Messiah!
- See Deuteronomy 32:16 and Isaiah 44:14, which use the same term for abomination to refer to idols.
Source: First Fruits of Zion