This refers to the Jewish people who follow Law of Moses.
## those who are from Abraham's faith ##
This refers to those who have faith like Abraham did before he was circumcised.
## father of us all ##
Here the word "us" refers to Paul and includes all Jewish and non-Jewish believers in Christ. Abraham is the physical ancestor of the Jewish people, but he is also the spiritual father of those who have faith. (See: [[rc://en/ta/man/translate/figs-inclusive]])