"Why Passover?"

"When Abraham, the first Hebrew, left Ur to follow God's call, he sacrificed a life of comfort and ease. Ur was no small village. It was one of the oldest, most important cities of Mesopotamia, covering an area of about four square miles by the Euphrates River, which empties into the Persian Gulf. The citizens of Ur, numbering well over half a million, lived in walled safety. The enjoyed the advantages of the highest culture and civilization of their time. The outstanding architecture of their temples, which they built in honor of their numerous deities, was a source of great pride. From the comfort, advantages, and sophistication of Ur, Jehovah called Abraham and his family to a semi nomadic way of life. They were not nomads in spirit, for they were headed to the Promised Land, but they did not yet possess it. They wandered with the seasons, seeking pasture for their flocks, and they also tilled the ground. Tents were their only shelter from the scorching sun and cruel desert wind. But they believed that one day the land really would be theirs, evidenced by their burying those who died along the way in the permanent caves. Then a great drought and famine drove Jacob, a grandson of Abraham, to leave Canaan for the promises of food in Egypt. Once again the seed of Abraham dismantled their tents. Packing all that they had left, they headed south with their wives, their little ones, and their flocks. Because Jacob's son Joseph had found favor with the current pharaoh, they were welcomed as honored guests and given the land of Goshen as their dwelling place (Genesis 47:6). Goshen was a fertile area along the delta of the Nile River, lying in the Northeast portion of an area between what is now Cairo and to the southeast and Alexandria to the northwest. Here the Hebrews felt respected and secure." (Ciel and Moishe Rosen, Christ in the Passover)

From this last trek to food, and the blessing that came from it, the descendants of Abraham prospered for hundreds of years. They had no worries or cares. Everything survived, bleats and bellows of starvation were no more. However, there arose a new pharaoh who "did not know about Joseph" (Exodus 1:8)

This new Pharaoh believed that there were more Israelites than Egyptians and decided to do something about it. Enslaving the Israelites, he desired to kill all of them off by literally working them to death. He would give them projects that were insurmountable, having his slave-drivers whip those who did not meet the criteria. 

The Israelites began to cry out to God, seeking Him for rescue. God raised up a man by the name of Moses to deliver His people. As Moses wielding his staff bellowed "Let my people go!" the new Pharaoh refused and only pushed the Israelites harder. 

Through Moses, God demonstrated His power, bringing plague after plague to change Pharaoh's mind--but he only hardened it more and more toward the Israelites. The last plague was the specter of death, taking all of the firstborn children, interrupting the line of inheritance. Fear would wash over those who did not fear or obey God. 

The Israelites were instructed to bring in a lamb for four days and then slaughter the lamb. The blood of the lamb was to go on the door frames of the houses, and when the angel of death went through, the blood would be a sign that death was to pass over that home. (Exodus 12:3, 6-7, 12-13)

"The word used...in this sense in Isaiah 31:5: "As birds flying, so with the Lord of Hosts defend Jerusalem; defending also He will deliver it; and passing over (pasoach, participle of pasach) He will preserve it." the word has, consequently, the very meaning of the Egyptian term for "spreading the wings over and protecting"; and peach, the Lord's passover, means such sheltering and protection as is found under the outstretched wings of the Almighty. Does this not give a new fullness to those words "O Jerusalem! Jerusalem!... How often would I have gathered thy children together, as a hand does gather her brood under her wings?" (Luke 13:34).. and this term pesach is applied to the ceremony...and to the lamb...the slain lamb, the sheltering behind its blood and eating of its flesh, constituted the pesach, the protection of God's chosen people beneath the sheltering wings of the Almighty... It was not merely that the Lord passed by the houses of Israelites, but that He stood on guard protecting each blood-sprinkled door!" (Arthur W. Pink, Gleanings in Exodus)

The passover lamb foreshadowed the One to come who would be God's final means of redemption and atonement: JESUS. 

The sinless, spotless blood of the Lamb of God who takes away the sin of the world (John 2) is the atonement and redemption that must be applied to the doorposts of our hearts so that God stands guard and protects us from the angel of death. Without Passover, the resurrection of Jesus would be insufficient---the Lamb slain was the atonement, Jesus raised from the dead was the redemption that gave us our heavenly inhertiances.