Genesis 17:13 (NIV)
Whether born in your household or bought with your money, they must be circumcised. My covenant in your flesh is to be an everlasting covenant.
Leviticus 24:8 (NRSV)
Every sabbath day Aaron shall set them in order before the LORD regularly as a commitment of the people of Israel, as a covenant forever.
The covenants between God and the Jews are considered forever/everlasting for a reason, that is, from a legal/lawful point of view. There's a bonding between God and those Jews remaining loyal to Him. This is indicative of the Jewish circumcision and Sabbath keeping (they are not a requirement of the gentile Christians, or not part of the New Covenant in a broader sense). If a Jewish Christian would like to keep this bonding between God and the Jews in a forever sense, he needs to be circumcised and to keep the Sabbath as a basic requirement of this forever/everlasting covenant.
That's why even Paul urged Timothy to be circumcised. By bloodline Timothy's mother is a Jew. Paul not only wanted Timothy to be a Christian, but also wanted him to be a Jew to be circumcised. This however is never a requirement of any gentile Christians.
I understand the notion that "only circumcised inwardly counts". However it doesn't seem that this doctrine fits what the Bible explicitly expresses.
In today's world, there are still 2 million orthodox Jews (out of the 20 million Jewish population) trying to abide by the Mosaic Law and Jewish customs, including circumcision and Sabbath keeping. It by no means says that God accepts today's Judaism (they are not considered saved by the standard specified through the Mosaic Law). It however says that they are still loyal to God, though they failed to recognize their own Messiah.
"Balaam" is also defined for them. Whoever Jews standing in the way of God's salvation are not counted as a Jew.
Revelation 3:9 (NIV)
I will make those who are of the synagogue of Satan, who claim to be Jews though they are not, but are liars—I will make them come and fall down at your feet and acknowledge that I have loved you.
In a nutshell, God's bonding with the Jews is a forever bonding. The Jews are those circumcised and keeping the Law (Mosaic Law). They are however not counted as a Jew if they choose to stand in the way of God's salvation through Jesus Christ.
While apparently they are not saved by observing the Mosaic Law to an acceptable standard, God may still have mercy on them (some of them to be more specific) from a legal/lawful point of view.
I appreciate your scholarship and thorough response; however, so long as we do not read prophecy of Scripture through the clear glass of NT teaching of Scripture, we will remain as loyal to a false interpretation of prophecy, as them that try to remain loyal to a covenant and law that is passed:
It is the spirit that quickeneth; the flesh profiteth nothing: the words that I speak unto you, they are spirit, and they are life.
The covenants between God and the Jews are considered forever/everlasting for a reason, that is, from a legal/lawful point of view. There's a bonding between God and those Jews remaining loyal to Him.
And when the everlasting God of Israel was crucified on the cross, then that bond by covenant and law was broken and done away.
The first covenant was of flesh, both by birth and circumcision, as was also the law of a carnal commandment that made it (Heb 7:16), and now none of it is profitable with the risen God of Israel.
Yea doubtless, and I count all things but loss for the excellency of the knowledge of Christ Jesus my Lord: for whom I have suffered the loss of all things, and do count them but dung, that I may win Christ.
Outward circumcision is now but dung with God.
If a Jewish Christian would like to keep this bonding...
There is no such thing as a 'Jewish Christian' in scripture. That was the error of the Galatian Christians, who were bewitched into trying to become 'Jewish Christians' by circumcision of flesh, and was causing them to fall from grace of God.
Paul needed rebuke Peter, who was also trying to remain a 'Jewish Christian'.
That's why even Paul urged Timothy to be circumcised.
Falling from grace to become a "Jewish Christian' was why it was sentenced that none need be circumcised outwardly for any reason.
Timothy then became willingly circumcised to remove a ministerial thorn of the flesh, when ministering to unbelieving Jews, who would never listen to the uncircumcised in the flesh, much less allow them into their synagogues of Satan.
I understand the notion that "only circumcised inwardly counts". However it doesn't seem that this doctrine fits what the Bible explicitly expresses.
It is not a notion, but an explicitly written Scriptural truth of the only circumcision that now counts with God:
Neither is that circumcision, which is outward in the flesh...circumcision is that of the heart, in the spirit, and not in the letter; whose praise is not of men, but of God.
There is now only one circumcised people on earth, and that is them walking in natural bodies with the circumcision of Christ inwardly. (Col 2:11)
They are the only remnant of the last days being built again from scratch as the tabernacle of David (Acts 15), which the risen Lord now pitches on earth. (Heb 8:2)
"Balaam" is also defined for them. Whoever Jews standing in the way of God's salvation are not counted as a Jew.
All flesh is now 'Balaam' to God, without respect of persons with God, especially them worshipping in a false religion with a profaned circumcision and Sabbath, supposing themselves 'loyal' to the God of Israel, whom they slew by unbelief:
For ye, brethren, became followers of the churches of God which in Judaea are in Christ Jesus: for ye also have suffered like things of your own countrymen, even as they have of the Jews: Who both killed the Lord Jesus, and their own prophets, and have persecuted us; and they please not God, and are contrary to all men: Forbidding us to speak to the Gentiles that they might be saved, to fill up their sins alway: for the wrath is come upon them to the uttermost. (I Thess 2)
I will make those who are of the synagogue of Satan, who claim to be Jews though they are not, but are liars.
All who call themselves 'Jews' by outward circumcision are liars before God, because there is no more circumcision of flesh with God. No matter what day of the week, especially not the 8th day after birth in order to keep a law of Moses and old covenant, that the risen God of Israel no longer acknowledges as His own.
In today's world, there are still 2 million orthodox Jews (out of the 20 million Jewish population) trying to abide by the Mosaic Law and Jewish customs, including circumcision and Sabbath keeping.
And there are millions of Muslims trying to abide by Sharia law and muslim customs out of the old covenant, including circumcision and Sabbath keeping.
And neither have any honor with God. Such 'loyalty' and righteousness of man is foolishness with God, and as filthy rags, and is called by Paul will worship:
Which things have indeed a shew of wisdom in will worship, and humility, and neglecting of the body; not in any honour to the satisfying of the flesh. (Col 2)
They satisfy the flesh and pride of a willful religion, but with no honor to God.
Zeal in a good thing is good (Gal 4:18), but zeal in a lie is refusing the righteousness of God by faith, in order to remain loyal to one's own righteousness sought without Scripture of God.
They need to be zealous; therefore, and repent, because no man has any promise nor bond nor favor with God in the flesh.
'Loyalty' is not a Bible word. Being sincerely wrong doesn't make it good, especially when it led to crucifying the Lord of glory. Zealously so.