diff --git a/exo/07/03.md b/exo/07/03.md
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 # harden Pharaoh's heart
 
-"will cause Pharaoh to be stubborn". Pharaoh's heart is often described as hard in this chapter. This means that his heart was not open or willing to understand Yahweh's instructions. When his heart was hardened, it became less and less receptive to Yahweh. 
+"will cause Pharaoh to be stubborn". Pharaoh's heart is often described as hard in this chapter. This means that his heart was not open or willing to understand Yahweh's instructions. When his heart was hardened, it became less and less receptive to Yahweh. (see Exodus 4:21)
 
 # many signs ... many wonders