'Firstling' in the Bible

“You shall consecrate (set apart) to the Lord your God all the firstborn males that are born of your herd and flock. You shall not work with the firstborn of your herd, nor shear the firstborn of your flock.

“His majesty is like a firstborn young bull,And his horns like the horns of the wild ox;With them he will gore the peoples,All of them together, to the ends of the earth.And those are the ten thousands of Ephraim,And those are the thousands of Manasseh.”