One reason I went into such detail about the plagues is to show whoever wrote the Exodus account had an intimate knowledge of the Egyptian religion. It was not just a simple story of 10 bad things happening as children’s Sunday school lessons typically portray. Readers that lived in the Egyptian New Kingdom period would’ve understood the deeper religious meaning for the plagues. As mentioned in post 1005, “hardening of Pharaoh’s heart” is mentioned at least 20 times in the account. Obviously the writer is emphasizing this point. Readers that are not familiar with Egyptian religion and the Hebrew language will overlook the deeper meaning of this. The better translation should be “Pharaoh’s heart was made heavier”. This was in reference to people who died will be judged by weighing their heart against maat.
Maat or Maʽat (Egyptian: mꜣꜥt /ˈmuʀʕat/, Coptic: ⲙⲉⲓ) refers to the ancient Egyptian concepts of truth, balance, order, harmony, law, morality, and justice.
Maat represents the ethical and moral principle that all Egyptian citizens were expected to follow throughout their daily lives. They were expected to act with honor and truth in matters that involve family, the community, the nation, the environment, and the god.
And it was the responsibility of the Pharaoh to uphold maat.
“Pharaohs are often depicted with the emblems of Maat to emphasise their roles in upholding the laws and righteousness.”
Through each successive plague, there was less order and Pharaoh was powerless to maintain harmony. In addition, he would be judged in the afterlife that he failed to live up to maat. Each plague was against a major god of the Egyptians with many of them having a role in the weighing of the heart.
How could anyone writing in the time of the post-Babylonian captivity would’ve had such knowledge of the Egyptian religion? And even if someone did, why would he write it when practically nobody else would’ve understood the deeper meaning? It makes more sense that it was written in the New Kingdom period where everyone fully understood the deeper religious meaning.