Tsze-kung asked, saying, “Is there one word which may serve as a rule of practice for all one’s life?” The Master said, “Is not RECIPROCITY such a word? What you do not want done to yourself, do not do to others.”

Confucius (551-479 BC) Chinese philosopher [Ku'ng Ch'iu / King Qiu, Ku'ng Fu-tzu / Kong Fuzi]
The Analects [Lun Yü], 15.24 (6th C. BC) [ed. Lao-Tse; tr. Legge (1930)]
    (Source)

Alt. trans.:

• Zigong asked: "Is there any single word that could guide one's entire life?" The Master said: "Should it not be reciprocity? What you do not wish for yourself, do not do to others." [tr. Leys (1997)]
• Zigong asked: "Is there a single word that can serve as the guide to conduct throughout one's life?" The Master said, "It is perhaps the word shu. Do not impose on others what you yourself do not want." [tr. Chin (2014); Chin translates shu as "treating others with an awareness that they, too, are alive with humanity"]
• Zi-gong asked: "Is there one single word that one can practice throughout one's life?" The Master said: "It is perhaps 'like-hearted considerateness.' 'What you do not wish for yourself, do not impose on others.'" [tr. Huang (1997)]
• "Do not do to others what you do not want them to do to you."

See also the Bible, Matthew 7:12.