From
《论语·卫灵公》 (Analects, Wei Ling Gong chapter, ~5th-4th c. BCE):
君子义以为质,
礼以行之 (The gentleman takes righteousness as substance, acts on it through ritual, expresses it with modesty, completes it with trustworthiness). A core Confucian definition of
君子 in four clauses.