Then would you explain Gal 2:16 which says "faith of Christ"?
The Greek "dia pistewv Ihsou Xristou"
Dia:
through
of place
with
in
of time
throughout
during
of means
by
by the means of
through
the ground or reason by which something is or is not done
by reason of
on account of
because of for this reason
therefore
on this account
So by means of Pistis:
conviction of the truth of anything, belief; in the NT of a conviction or belief respecting man's relationship to God and divine things, generally with the included idea of trust and holy fervour born of faith and joined with it
relating to God
the conviction that God exists and is the creator and ruler of all things, the provider and bestower of eternal salvation through Christ
relating to Christ
a strong and welcome conviction or belief that Jesus is the Messiah, through whom we obtain eternal salvation in the kingdom of God
the religious beliefs of Christians
belief with the predominate idea of trust (or confidence) whether in God or in Christ, springing from faith in the same
fidelity, faithfulness
the character of one who can be relied on
We now have by means of belief (Faith) or conviction in of Iesous Jesus or Joshua as the Hebrew would be, Christos Christ,
Gal. 2:16 "Faith of Christ" is redendered from the Greek, through conviction or belief that Jesus Christ is the Messiah through whom we obtain eternal life. The Textus Receptus bears it out, that is what the KJV is translated from.