In the old testament things were done physically that are now done spiritually in the new testament.
That is not what Paul, nor Jesus said, see:
Rom_7:14 For we know that
the law is spiritual: but I am carnal, sold under sin.
Rom_8:7 Because
the carnal mind is enmity against God: for it is not subject to the law of God,
neither indeed can be.
The Law of God was always spiritual, and could only, and ever, be kept by those walking in the Spirit:
Gal_5:16 This I say then, Walk in the Spirit, and ye shall not fulfil the lust of the flesh.
Gal_5:25 If we live in the Spirit, let us also walk in the Spirit.
Rom_8:4 That
the righteousness of the law might be
fulfilled in us,
who walk not after the flesh,
but after the Spirit.
The Law of God is spiritual, all of it, and was written by the Son of God, by the Holy Ghost (Matthew 12:28; Luke 11:20):
Exo_31:18 And he gave unto Moses, when he had made an end of communing with him upon mount Sinai, two tables of testimony, tables of stone,
written with the finger of God.
Deu_9:10 And the LORD delivered unto me two tables of stone
written with the finger of God; and on them was written according to all the words, which the LORD spake with you in the mount out of the midst of the fire in the day of the assembly.
God always required all the heart, from the beginning:
Deu_10:16 Circumcise therefore the foreskin of your heart, and be no more stiffnecked.
Deu_30:6 And the LORD thy God will circumcise thine heart, and the heart of thy seed, to love the LORD thy God with all thine heart, and with all thy soul, that thou mayest live.
Jer_4:4 Circumcise yourselves to the LORD, and take away the foreskins of your heart, ye men of Judah and inhabitants of Jerusalem: lest my fury come forth like fire, and burn that none can quench it, because of the evil of your doings.
Rom_2:28 For he is not a Jew, which is one outwardly; neither is that circumcision, which is outward in the flesh:
Rom_2:29 But he is a Jew, which is one inwardly; and circumcision is that of the heart, in the spirit, and not in the letter; whose praise is not of men, but of God.
Rom_15:8 Now I say that Jesus Christ was a minister of the circumcision for the truth of God, to confirm the promises made unto the fathers:
Php_3:3 For we are the circumcision, which worship God in the spirit, and rejoice in Christ Jesus, and have no confidence in the flesh.
Col_2:11 In whom also ye are circumcised with the circumcision made without hands, in putting off the body of the sins of the flesh by the circumcision of Christ:
Notice the parallels:
1Co_7:19 Circumcision is nothing, and uncircumcision is nothing, but
the keeping of the commandments of God.
Gal_5:6 For in Jesus Christ neither circumcision availeth any thing, nor uncircumcision; but
faith which worketh by love.
Gal_6:15 For in Christ Jesus neither circumcision availeth any thing, nor uncircumcision, but
a new creature.
Outward formality, without inward sanctification by the Holy Ghost, could never keep God's commandments, especially the Sabbath, which encompasses every day, which is why 'Israel after the flesh", continually transgressed the Sabbath Commandment (Exodus 20:8-11), see Hebrews 3-4. They (Israel after the flesh) had the right day of rest (the 7th day, of the Lord), but the wrong heart, and thus never truly entered into the rest of God (Genesis 2:1-3). Hebrews 3-4 is citing many OT texts. If you would like, I can post a study on each verse of Hebrews 3-4.