The event you’re referring to is known as the Passover, which is detailed in the Book of Exodus. It represents the final of the ten plagues that God inflicted upon Egypt, as recorded in Exodus 11:1-5 and Exodus 12:29-30. The reason behind this judgment was Pharaoh’s continued refusal to release the Israelites from slavery, despite Moses’s repeated requests in God’s name. Each plague, culminating in the death of the firstborn sons, demonstrated not only God’s power but also the impotence of the Egyptian gods and the injustice of Israel’s oppression.

God instructed the Israelites to mark the doorposts of their homes with the blood of a sacrificed lamb and promised that when He saw the blood, He would “pass over” those homes, sparing them from this final plague. This event is commemorated by the Jewish festival of Passover, celebrating deliverance from slavery in Egypt.

This severe action was not taken lightly but came after multiple warnings and lesser plagues, all aimed at securing the freedom of the Israelite people without this ultimate tragedy. It underscores themes of justice, liberation, and the consequences of hard-heartedness towards the divine will.

“And the LORD said unto Moses, Pharaoh shall not hearken unto you; that my wonders may be multiplied in the land of Egypt.” (Exodus 11:9). God’s purpose, as difficult as it may be to comprehend, was to reveal His power and establish a narrative of deliverance and covenant relationship with His people, which would guide them and their understanding of God’s character throughout their history.