Here "heart" refers to the Pharaoh. His stubborn attitude is spoken of as if his heart was hard. See how you translated a similar phrase in [Exodus 9:12](../09/12.md). Alternate translation: "I will cause Pharaoh to became more defiant" (See: [[rc://en/ta/man/jit/figs-synecdoche]] and [[rc://en/ta/man/jit/figs-metaphor]])
This can be stated in active form. Alternate translation: "So the Israelites camped as Yahweh had instructed them" (See: [[rc://en/ta/man/jit/figs-activepassive]])