Afterward Moses and Aaron went and said to Pharaoh, “Thus says the Lord, the God of Israel, ‘Let my people go, that they may hold a feast to me in the wilderness.’” But Pharaoh said, “Who is the Lord, that I should obey his voice and let Israel go? I do not know the Lord, and moreover, I will not let Israel go.”
Pharaohs saw themselves as gods and as the givers of divine law and mandates. When ADONAI sent Moses to have Pharoah release the Hebrews, the Pharaoh viewed this as an insult to his perceived worldly divine authority. The Pharaoh knew who Moses was which made it even more offensive demanding the release of Egypt's largest
non-union brick producing collective.