Exo 13:1 And the LORD spake unto Moses, saying,
Exo 13:2 Sanctify unto me all the firstborn, whatsoever openeth the womb among the children of Israel, both of man and of beast: it is mine.
Num 3:13 Because all the firstborn are mine; for on the day that I smote all the firstborn in the land of Egypt I hallowed unto me all the firstborn in Israel, both man and beast: mine shall they be: I am the LORD.
All the firstborn of Egypt were killed by the angel of death; all but the Children of God who applied the blood of the lamb to the doorposts, there were none of their firstborn killed. The firstborn male child of Israel were sanctified unto the LORD. This practice continues and it pointed to the sanctified firstborn Son of God, who came through the virgin Mary.
Mat 1:23 Behold, a virgin shall be with child, and shall bring forth a son, and they shall call his name Emmanuel, which being interpreted is, God with us.
Mat 1:24 Then Joseph being raised from sleep did as the angel of the Lord had bidden him, and took unto him his wife:
Mat 1:25 And knew her not till she had brought forth her firstborn son: and he called his name JESUS.
Jesus is the firstborn of a new spirit man.
2Co 5:17 Therefore if any man be in Christ, he is a new creature: old things are passed away; behold, all things are become new.
Paul shows Christ as being preeminent in God's plan of redemption because He is the Savior and Redeemer.
Rom 8:29 For whom he did foreknow, he also did predestinate to be conformed to the image of his Son, that he might be the firstborn among many brethren.
Rom 8:30 Moreover whom he did predestinate, them he also called: and whom he called, them he also justified: and whom he justified, them he also glorified.
Rom 8:31 What shall we then say to these things? If God be for us, who can be against us?
Jesus is the firstborn over all creation, Lord of all and head of the church.
Col 1:12 Giving thanks unto the Father, which hath made us meet to be partakers of the inheritance of the saints in light:
Col 1:13 Who hath delivered us from the power of darkness, and hath translated us into the kingdom of his dear Son:
Col 1:14 In whom we have redemption through his blood, even the forgiveness of sins:
Col 1:15 Who is the image of the invisible God, the firstborn of every creature:
Col 1:16 For by him were all things created, that are in heaven, and that are in earth, visible and invisible, whether they be thrones, or dominions, or principalities, or powers: all things were created by him, and for him:
Col 1:17 And he is before all things, and by him all things consist.
Col 1:18 And he is the head of the body, the church: who is the beginning, the firstborn from the dead; that in all things he might have the preeminence.
Col 1:19 For it pleased the Father that in him should all fulness dwell;
The firstborn male child of Israel is sanctified unto the LORD and received a double portion of the physical inheritance of the family. The firstborn of the anmal flock were prized as sacrifices. Jesus the firstborn is God the Son and the Lamb of God who was sacrificed for our sins. Being holy and preeminent Jesus returned to the Father in Glory and he is the Great High Priest and the head of the church body.