From the Analects (
《论语·里仁》): when a disciple asked what tied Confucius's teaching together, Zengzi (
曾子) answered 'the Master's Way is just
忠恕, nothing more' (
夫子之道,忠恕而已矣).
恕 was famously glossed by Confucius as
己所不欲,勿施于人 - the Golden Rule in negative form.