Exodus 4:23
Let my son go, that he may serve me - Which they could not do in Goshen, consistently with the policy and religious worship of the Egyptians; because the most essential part of an Israelite' s worship consisted in sacrifice, and the animals which they offered to God were sacred among the Egyptians. Moses gives Pharaoh this reason Exodus 8:26.
I will slay thy son, even thy first-born - Which, on Pharaoh' s utter refusal to let the people go, was accordingly done; see Exodus 12:29.
