Luke 2:23

in fulfilment of the requirement of the Law of the Lord, "Every first-born male shall be considered consecrated to the Lord,"

Hebrews 12:23

to the solemn gathering of all God's elder sons, enrolled as citizens in heaven, to a judge who is the God of all, to the spirits of upright men now at last enjoying the fulfilment of their hopes,

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
in fulfilment of the requirement of the Law of the Lord, "Every first-born male shall be considered consecrated to the Lord,"
Hebrews 12:23
to the solemn gathering of all God's elder sons, enrolled as citizens in heaven, to a judge who is the God of all, to the spirits of upright men now at last enjoying the fulfilment of their hopes,