They are both tokens of a covenant with God.
The individual Iraelite in the OT who was not circumcised, though born of Abraham , was cut off from the covenant and was a cast away. God took this serious and at the end of this post I will show you from the scriptures how serious.
The Jews in the NT at the institution of the New Covenant who refused to believe and be born into the family of God were cast out of their land and cut off from the covenant. This was very serious sin.
Ex 4:20 And Moses took his wife and his sons, and set them upon an ass, and he returned to the land of Egypt: and Moses took the rod of God in his hand.
21 And the Lord said unto Moses, When thou goest to return into Egypt, see that thou do all those wonders before Pharaoh, which I have put in thine hand: but I will harden his heart, that he shall not let the people go.
22 And thou shalt say unto Pharaoh, Thus saith the Lord, Israel is my son, even my firstborn:
23 And I say unto thee, Let my son go, that he may serve me: and if thou refuse to let him go, behold, I will slay thy son, even thy firstborn.
24 A
nd it came to pass by the way in the inn, that the Lord met him, and sought to kill him.
25 Then Zipporah took a sharp stone, and cut off the foreskin of her son, and cast it at his feet, and said, Surely a bloody husband art thou to me.
26 So he let him go: then she said, A bloody husband thou art, because of the circumcision.
Acts 28:17 And it came to pass, that after three days Paul called the chief of the Jews together: and when they were come together, he said unto them, Men and brethren, though I have committed nothing against the people, or customs of our fathers, yet was I delivered prisoner from Jerusalem into the hands of the Romans.
18 Who, when they had examined me, would have let me go, because there was no cause of death in me.
19 But when the Jews spake against it, I was constrained to appeal unto Caesar; not that I had ought to accuse my nation of.
20 For this cause therefore have I called for you, to see you, and to speak with you: because that for the hope of Israel I am bound with this chain.
21 And they said unto him, We neither received letters out of Judaea concerning thee, neither any of the brethren that came shewed or spake any harm of thee.
22 But we desire to hear of thee what thou thinkest: for as concerning this sect, we know that every where it is spoken against.
23 And when they had appointed him a day, there came many to him into his lodging; to whom he expounded and testified the kingdom of God, persuading them concerning Jesus, both out of the law of Moses, and out of the prophets, from morning till evening.
24 And some believed the things which were spoken, and some believed not.
25 And when they agreed not among themselves, they departed, after that Paul had spoken one word, Well spake the Holy Ghost by Esaias the prophet unto our fathers,
26 Saying, Go unto this people, and say, Hearing ye shall hear, and shall not understand; and seeing ye shall see, and not perceive:
27 For the heart of this people is waxed gross, and their ears are dull of hearing, and their eyes have they closed; lest they should see with their eyes, and hear with their ears, and understand with their heart, and should be converted, and I should heal them.
28 Be it known therefore unto you, that the salvation of God is sent unto the Gentiles, and that they will hear it.
In a short time after this the dispersion out of their land took place in 70 AD.It lasted for nearly 2000 years.
