'First born' in the Bible

Then you shall say to Pharaoh, ‘Thus says the Lord, “Israel is My son, My firstborn.

So I said to you, ‘Let My son go that he may serve Me’; but you have refused to let him go. Behold, I will kill your son, your firstborn.”’”

These are the heads of their fathers’ households. The sons of Reuben, Israel’s firstborn: Hanoch and Pallu, Hezron and Carmi; these are the families of Reuben.

and all the firstborn in the land of Egypt shall die, from the firstborn of the Pharaoh who sits on his throne, even to the firstborn of the slave girl who is behind the millstones; all the firstborn of the cattle as well.

For I will go through the land of Egypt on that night, and will strike down all the firstborn in the land of Egypt, both man and beast; and against all the gods of Egypt I will execute judgments—I am the Lord.

Now it came about at midnight that the Lord struck all the firstborn in the land of Egypt, from the firstborn of Pharaoh who sat on his throne to the firstborn of the captive who was in the dungeon, and all the firstborn of cattle.

“Sanctify to Me every firstborn, the first offspring of every womb among the sons of Israel, both of man and beast; it belongs to Me.”

But every first offspring of a donkey you shall redeem with a lamb, but if you do not redeem it, then you shall break its neck; and every firstborn of man among your sons you shall redeem.

It came about, when Pharaoh was stubborn about letting us go, that the Lord killed every firstborn in the land of Egypt, both the firstborn of man and the firstborn of beast. Therefore, I sacrifice to the Lord the males, the first offspring of every womb, but every firstborn of my sons I redeem.’

“You shall not delay the offering from your harvest and your vintage. The firstborn of your sons you shall give to Me.

You shall redeem with a lamb the first offspring from a donkey; and if you do not redeem it, then you shall break its neck. You shall redeem all the firstborn of your sons. None shall appear before Me empty-handed.