Romans 8:29

For those whom God chose from the first he also destined from the first to be transformed into likeness to his Son, so that his Son might be the eldest among many Brothers.

Hebrews 12:23

to the festal gathering and assemblage of God's Eldest Sons whose names are enrolled in Heaven, to God the Judge of all men, to the spirits of the righteous who have attained perfection,

Treasury of Scripture Knowledge

Summary

All the firstling males that come of thy herd and of thy flock thou shalt sanctify unto the LORD thy God: thou shalt do no work with the firstling of thy bullock, nor shear the firstling of thy sheep.

The firstling

Bible References

The firstling

Romans 8:29
For those whom God chose from the first he also destined from the first to be transformed into likeness to his Son, so that his Son might be the eldest among many Brothers.
Hebrews 12:23
to the festal gathering and assemblage of God's Eldest Sons whose names are enrolled in Heaven, to God the Judge of all men, to the spirits of the righteous who have attained perfection,