'First born' in the Bible

When he smote all the firstborn in Egypt, the most principal and mightiest in the dwellings of Ham.

And I will make him my firstborn, higher than the kings of the earth.

He smote all the firstborn in their land, even the chief of all their strength.

He smote the firstborn of Egypt, both of man and of beast.

Which smote Egypt with their firstborn! For his mercy endureth forever.