en_tn/rom/02/28.md

outwardly

This refers to Jewish rituals, such as circumcision, which people can see.

merely outward in the flesh

This refers to the physical change to a man's body when someone circumcises him.

flesh

This is a synecdoche for the whole body. AT: "body" (See: rc://en/ta/man/translate/figs-synecdoche)