In Leviticus 12:3 what was the symbolic significance of choosing the eighth day after birth for the time of circumcision?
[Lev 12:3 KJV] (3) And in the eighth day the flesh of his foreskin shall be circumcised.
In a compilation made in mid-13th century France by Chizkuni, there is an explanation quoting Rabbi Shimon ben Yochai, that the 8th day had been chosen by God for circumcision of the newly born so that the whole family could rejoice in that celebration. Otherwise, the mother of the child could not be part of it due to her still being ritually unclean:
Leviticus 12:2 Say to the Israelites: 'A woman who becomes pregnant and gives birth to a son will be ceremonially unclean for seven days, just as she is unclean during her monthly period. (NIV)
On the other hand, in the same Chizkuni's compilation, it is underlined that this commandment is so important that it can be performed on the eighth day, that it overrides the work prohibition on the Sabbath. Only preparatory activities associated with the circumcision are forbidden even on the Sabbath, whereas the circumcision itself overrides the Sabbath provided it is performed on the eighth day. [For more please see Chizkuni, Leviticus 12:3:2; also in Shabbat 132a:1, 132a:13]
Then, the 8th-day circumcision becomes a sort of a model for any animal sacrifice:
Leviticus 22:27 When a calf, a lamb or a goat is born, it is to remain with its mother for seven days. From the eighth day on, it will be acceptable as a food offering presented to the Lord. (NIV)
So, there are 4 meaningful things here:
But this is not it. There is another very interesting thing, we are approaching the symbolic significance of the 8th-day circumcision: in a Midrash on Leviticus 12:3, this is related to Leviticus 22:27 (above) and to Ecclesiates 3:19.
Ecclesiastes 3:19 Surely the fate of human beings is like that of the animals; the same fate awaits them both: As one dies, so dies the other. All have the same breath; humans have no advantage over animals. Everything is meaningless. (NIV)
But for the end of Eccl. 3:19, this Midrash is going:
Midrash Tanchuma Buber, Emor 21:1: ... as the one dies, so does the other die. They all have the same lifebreath, but the superiority of the human over the beast is nil ('YN). This is the translation required by the latter part of this section. [...] Because the lifebreath of the human is given from above, concerning it a rising up is written. And because the beast is given from below, concerning it a going down is written (Eccl. 3:21). […] And what is the meaning of 'YN? It is that < the human > speaks, but < the beast > does not ('YN) speak. And moreover, while there is knowledge in the human, in the beast there is no ('YN) knowledge. And moreover, while the human knows the difference between good and evil, the beast does not ('YN) know the difference between good and evil. And moreover, the human gets a reward for his works, but the beast does not ('YN) get a reward for its work. And moreover, when the human dies they care for him and he is buried, while the beast is not ('YN) buried.
Now to the 4 above, we can add a 5th symbolical meaning:
As a conclusion, if we sum up 1 > 5 and try reading Leviticus 12:3 + Leviticus 22:27 in the light of Eccl. 3:19, the symbolical meaning would be:
On the 8th day: circumcision & joy, so that everybody may join in.
From the 8th day, animals good for a sacrifice
Humans and animals are both mortals
Finally, circumcision on the 8th day, overriding Sabbath prohibitions, because it is about human “putting off the body of the flesh”, and taking on his spiritual status. That would be, I think, the symbolical meaning.
My own understanding of this is that seven days is the full time of creation, six days of creating work and one day of rest in that creation - a fulfilled accomplishment, a resting in that fulfilled activity.
But on that seventh day, Eve was deceived and Adam transgressed. And in the cool of the day, the evening, the sun now falling in the heavens, God walked (no longer at rest) and God spoke 'Adam, where art thou ?'
So another day began. A new creation. :
My Father worketh hitherto, and I work. [John 5:17 KJV.]
The ritual of circumcision is a matter of the removal of flesh. And that removal is associated with the manner of procreation, the passing on of sinful flesh to another generation.
But Abraham was circumcised before he had Isaac, so Isaac (in a figure) is born not of the flesh but of the spirit. A new creation.
It was the eighth day when Jesus rose, for it was the end of the sabbath, the sabbath was passed, Mark 16:1. A new day dawned, a new creation, a resurrection.
Therefore if any man be in Christ, he is a new creation: old things are passed away; behold, all things are become new. [II Corinthians 5:17 KJV.]