Why did the firstborn of the Egyptians have to die?

The Orthodox nuance

In Exodus, Pharaoh kills and oppresses. He repeatedly refuses to let the people go despite warnings. The death of the firstborn is presented as the final act of judgment on a power that made children, labor, and bodies its property.

This does not make the passage easy. A Christian should not read the death of the Egyptians as cruel satisfaction. The Church reads the episode especially typologically: the Passover lamb, the blood on the doors, the crossing of the sea — all point to Christ and to the exodus from slavery to sin and death.

In the New Covenant, other people's children are not the price of liberation. Christ, the Son and Firstborn, gives Himself. This does not erase the severity of the old text, but it shows where God's pedagogy leads: not toward killing the enemy, but toward the Son's sacrifice for the life of the world.