On the Shabbat before the Exodus--Nissan 10th on that year--the first-born of Egypt, who occupied the senior positions in the priesthood and government, fought a bloody battle with Pharaoh's troops, in an effort to secure the release of the Israelites and prevent the Plague of the Firstborn. This "great miracle" is commemorated each year on the Shabbat before Passover, which is therefore called Shabbat HaGadol, "The Great Shabbat." (This is one of the rare instances in which a commemorative date in the Jewish calendar is set by the day of the week rather than the day of the month.)
For more on the war of the Firstborn, see here.
Miriam, the sister of Moses, passed away at the age of 126 on the 10th of Nissan of the year 2487 from creation (1274 BCE) -- 39 years after the Exodus and exactly one year before the Children of Israel entered the Holy Land. It is in deference to her passing that the "Great Shabbat" is commemorated on the Shabbat before Passover rather than the calendar date of the miracle's occurence, Nissan 10.
Link: About Miriam.
Three days after the two spies dispatched by Joshua scouted the city of Jericho (see entry for "Nissan 7" above), the children of Israel were ready to enter the land promised by G-d to their ancestors as their eternal heritage. As they approached the Jordan with the Holy Ark carried by the Kohanim (priests) in their lead, the river parted for them, as the waters of the Red Sea had split when their fathers and mothers marched out of Egypt 40 years earlier. (Joshua 4)
In today's "Nasi" reading (see "Nasi of the Day" in Nissan 1), we read of the gift bought by the nasi of the tribe of Dan, Achiezer ben Amishadai, for the inauguration of the Mishkan.
The Shabbat before Passover is termed Shabbat HaGadol ("The Great Shabbat") in commemoration of the "great miracle" that happened in Egypt on this day, heralding the Exodus from Egypt five days later (see "Today in Jewish Hstory"). Shabbat HaGadol customs include reading a portion of the Haggadah (from "Avadim hayinu..." to "...al kol avonotainu"), which tells the story of the Exodus; it is also customary that the rabbi of the community delivers a lecture in which he elaborates on the laws of Passover and their significance, in preparation for the festival.
The great men who spied out the Land of Canaan returned and reported:
“We cannot go. They are stronger than us.”
They were brave, wise men, hand-picked by Moses. How could they have erred so disastrously?
Because, subconsciously, they never really wanted to leave the spiritual high of the desert for a life of tilling soil and building homes.
If they had only realized their true issue and asked Moses, he would have explained to them:
“This experience now is only the chrysalis. In the land, you will spread your wings.”
“From within these clouds of glory that surround us on our journey, you can perceive great light. There, in that earth, stone and clay, you will hold raw truth in your hands.”
And so to each of us Moses says:
Do not be afraid to emerge from your spiritual cocoon and enter that monstrous, formidable world.
As much as you can attain in your studies, even in deep contemplation and intense prayer, it will never come close to the wisdom that will open itself to you in your mission to build a home, give life, learn Torah, do mitzvahs, and lend a hand to others in a hostile universe.
Your eyes will see that which no book could tell, your heart will feel that which no thought could imagine.
In the joy that comes out of pain, in the sweetness that emerges from bitter suffering, this world will carry you to a place beyond anything your soul could otherwise have known.