Romans 14:5
One person considers one day more sacred than another; another considers every day alike. Each of them should be fully convinced in their own mind. — Krino (esteem, regard as distinct) hēmeran (day) distinctions possibly involves Sabbath observance or festival calendars. Plērophoreo (fully convince, fill completely) in his own dianoia (mind, reasoning) allows each conscience to operate. Conviction (pistis, faith) must be personally owned, not borrowed from others.