be honor-bound to (do something)
To be or feel obliged to do something because it is morally correct or required by one's sense of duty or integrity, even if one does not desire to do so. Primarily heard in US. It pains me to turn you in to the police, my friend, but I am honor-bound to inform them of your actions.
be/feel duty/honour ˈbound to do something
(British English) (American English be/feel duty/honor ˈbound to do something) (formal) feel that you must do something because of your sense of moral duty: She felt honour bound to attend as she had promised to.Most people think that children are duty bound to look after their parents when they are old.