The Shabbat before Pesach is called Shabbat Hagadol, for several reasons:
1. Because of the miracle that occured then.
The Jews were commanded to take a lamb on the tenth of Nissan which would serve as the Pesach sacrifice. On that year, the tenth came out on Shabbat. The Egyptians asked the people why
they were taking the lamb and they replied: In order to slaughter it for a Pesach sacrifice. The lamb was considered a deity by the Egyptians. Nevertheless, they did not harm the Jews, but remained silent.
2. On this Shabbat, we read the Haftara from Malachi Chapter 2:
This chapter ends with the verse: