Biblical Context:
The Plague on the Firstborn is the tenth and final plague that God inflicts upon Egypt, as recorded in the Book of Exodus. This event is a pivotal moment in the narrative of the Israelites' liberation from Egyptian bondage. The foretelling of this plague is found in Exodus 11, where God communicates His intentions to Moses, who then relays the message to Pharaoh.

Scriptural Account:
In Exodus 11:1-10, the Lord speaks to Moses, declaring that He will bring one more plague upon Pharaoh and Egypt. This plague will compel Pharaoh to release the Israelites from slavery. The Lord instructs Moses to tell the people to ask their Egyptian neighbors for articles of silver and gold, as they will find favor in the eyes of the Egyptians (Exodus 11:2-3).

The Lord then reveals the nature of the impending plague: "About midnight I will go throughout Egypt, and every firstborn son in the land of Egypt will die, from the firstborn of Pharaoh who sits on his throne to the firstborn of the servant girl behind the millstones, as well as all the firstborn of the cattle" (Exodus 11:4-5). This divine judgment is to be so severe that there will be a great cry throughout Egypt, unlike anything before or after (Exodus 11:6).

Theological Significance:
The Plague on the Firstborn serves as a profound demonstration of God's sovereignty and justice. It underscores the theme of divine retribution, as Pharaoh's persistent hardening of heart and refusal to release the Israelites culminate in this ultimate act of judgment. The death of the firstborn is a direct affront to the Egyptian belief system, which held the firstborn in high regard, often associating them with divine favor and inheritance.

This plague also highlights the distinction God makes between the Egyptians and the Israelites. In Exodus 11:7, it is stated, "But among all the Israelites, not even a dog will snarl at man or beast, so that you may know that the LORD makes a distinction between Egypt and Israel" . This distinction is a testament to God's covenantal faithfulness to His chosen people.

Cultural and Historical Context:
In ancient Egyptian culture, the firstborn held a place of prominence and were often seen as the primary heirs to family legacy and wealth. The death of the firstborn would have been a devastating blow to the social and familial structures of Egypt. Additionally, the inclusion of livestock in the plague's impact further emphasizes the comprehensive nature of God's judgment, affecting both human and economic resources.

Moses and Pharaoh:
Moses, as God's chosen leader, plays a crucial role in delivering the message of impending judgment to Pharaoh. Despite the severity of the warning, Pharaoh's heart remains hardened, fulfilling the pattern of resistance that characterizes his interactions with Moses and Aaron throughout the plagues. This hardening of heart is both a divine act and a personal choice, illustrating the complex interplay between divine sovereignty and human responsibility.

Implications for the Israelites:
For the Israelites, the foretelling of the Plague on the Firstborn is a moment of preparation and anticipation. It sets the stage for the Passover, where the Israelites are instructed to mark their doorposts with the blood of a lamb, ensuring that the angel of death passes over their homes (Exodus 12:7). This act of obedience and faith becomes a foundational element of Israelite identity and worship, commemorated annually in the Passover celebration.

Conclusion:
The Plague on the Firstborn Foretold is a critical juncture in the Exodus narrative, encapsulating themes of judgment, deliverance, and divine distinction. It serves as a powerful reminder of God's ultimate authority over nations and His unwavering commitment to His covenant people.