Luke 2:23

"Every first born male shall be counted consecrated to the Lord,"

Hebrews 12:23

to the festal gathering and assembly of God's firstborn sons enrolled as citizens in heaven, to a Judge who is the God of all, to the spirits of upright men who have attained perfection,

Treasury of Scripture Knowledge

Summary

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.

Bible References

Because

Luke 2:23
"Every first born male shall be counted consecrated to the Lord,"
Hebrews 12:23
to the festal gathering and assembly of God's firstborn sons enrolled as citizens in heaven, to a Judge who is the God of all, to the spirits of upright men who have attained perfection,