Regarding Hebrews 3, it says by means of sin hearts are hardened and that it can happen to "brothers".
Any man who has become a "son of God", SINS NO MORE.
Becoming a "son of God";
requires...A CONVERSION.
A Conversion, requires ...
HEARTFUL CONFESSION OF BELIEF IN God in Heaven "AND" Christ Jesus.
There ARE MANY "brethren" (JEWS), who BELIEVE in God, and "DO NOT BELIEVE in Christ Jesus, Son of God, their Messiah."
Yes, Jews CAN stop believing in God.
Yes, Jews CAN Never believe in Christ Jesus.
Yes, Gentiles can never believe in God, or In Christ Jesus.
Yes, Gentiles can stop believing in God, and In Christ Jesus.
ANY man who has HEARTFULLY Confessed Belief IN God "AND" Christ Jesus....SHALL Never Again (SIN)...Stop Believing IN God "AND" Christ Jesus....BECAUSE the POWER of God IS IN THEM, "MAKING" THEM FAITH-full, and KEEPING them IN BELIEF, and FAITHFUL to the Lord God Almighty. Never Again can they NOT BELIEVE.
Jews began being "BROTHERS" IN CHRIST...
THEN after the Apostals Died off...
Jews returned to Preaching God and waiting for their Messiah..."Keeping their Jewish LAW".
Some Jews have (MORE MODERNALY), BEGAN accepting Christ Jesus as their Messiah....they do not call themselves "Christians". They call themselves; "Messianic Jews".
Some Scripture IS precisely to JEWS, who were Under the Law, and Learning ABOUT Jesus.
Some Scripture IS precisely to GENTILES, who knew nothing about God or Jesus.
All Scripture does not apply the same to Every individual.
I am Converted.
My "brothers" are other individuals who ARE Converted.
My "brothers" are NOT Jews who are still under the Law, "not accepting" Christ Jesus.
Jesus has provided a WAY for all men to become Converted.
Many Gentiles Reject His offer.
Many Jews Reject His offer.
The Converted, are accounted as Christ's People.
The UnConverted STILL obeying the Jewish Law, are accounted as Gods People.
What Jesus has offered to His People is ...
FOREVER LIFE.
TO BE WITH HIM FOR EVER.
TO BE NOT SUBJECT TO ... WRATH.
TO BE NOT SUBJECT TO ... DAMNATION.
God has always "punished" His People for "disobedience"... Gods People Rejecting Christ Jesus IS "disobedience"... they shall Suffer, a small portion of Wrath...(expressly the Wrath of the Lamb) ...(and portions of the Wrath of the Devil).....
God has a plan FOR THEIR SALVATION, TO Learn About Christ Jesus, FROM "JEWS", (Gods Witnesses)...
They SHALL NOT SUFFER, Gods WRATH.