During the 16th century, the Dutch were fighting for independence from Spain, but their Spanish oppressors were not about to just let them go. Through many battles the Dutch struggled to be free. After one particularly bloody battle, Spanish soldiers took over the city of Rotterdam. They then went through the city systematically, house by house, slaughtering Dutch citizens and dragging their corpses out into the street. The people knew what was happening. They could hear the massacre going on all around them. Most simply waited in dread until the destruction reached their home. But one man had an idea. He killed a goat, collected its blood, and poured that blood on the floor inside the entryway to his house. Then, with a broom, he swept the blood under the door and out into the street. When the Spanish soldiers came to his house and noticed blood seeping out under the door, one of them said, "Let's move on. The work is already done at this place. Look at the blood marking the slaughter!" The Spanish soldiers moved on and the people inside the house marked with blood escaped death.
The scriptural account of the Passover in the book of Exodus tells a similar tale. The people of Israel had moved to Egypt during a famine. Hundreds of years later, they were slaves in a bad situation. They cried out to God to rescue them, and the Lord sent Moses to lead them out of slavery. Moses went to Pharaoh and told him to let God's people go. Pharaoh refused. God sent plagues upon the Egyptians to change Pharaoh's mind. Nine times God sent plagues, and nine times Pharaoh refused to free the Israelites. Finally, God told his people to pack up and get ready to travel. He was going to send one more plague. The tenth plague was an angel of death going through the country killing every firstborn male. But this death angel would pass over every household where the doorway was marked with the blood of a lamb. The Israelites dipped a hyssop branch into the blood of a sacrificed lamb and painted that blood on the top and sides of their door frames. When the death angel saw that blood, it passed over that home and spared the inhabitants. The homes without the blood were not so fortunate. This finally convinced Pharaoh. The next morning, the Israelite slaves left Egypt. Ever since, their descendants have remembered the Passover as their salvation event.
Years later, Jesus and his disciples gathered to celebrate Passover, remembering how their ancestors had been delivered. As they were there, they reflected on that deliverance of long ago. But Jesus was looking forward to an even greater deliverance. The next day he would sacrifice his blood. As the Israelites had stained the horizontal and vertical beams of their door frames with the blood of a lamb, the blood of the lamb of God would now stain the horizontal and vertical beams of a cross. He did this to make payment for your sin and my sin.
Those words of our Lord acknowledge our need for what he has to offer.