Here "heart" refers to Pharaoh. His stubborn attitude is spoken of as if his heart was hard. See how you translated this in [Exodus 7:13](../07/13.md). Alternate translation: "Pharaoh became more defiant" (See: [[rc://en/ta/man/translate/figs-synecdoche]] and [[rc://en/ta/man/translate/figs-metaphor]])
Here "the hand of Moses" is a metonym for Moses's activity in speaking. Yahweh had told Moses that Pharaoh would not let the people go, and Moses repeated it. Alternate translation: "just had Yahweh had said through Moses" or "just as Yahweh had said through Moses that Pharaoh would do" (See: [[rc://en/ta/man/translate/figs-metonym]])