Rooted in Confucian ethics.
《论语·卫灵公》 has
己所不欲,
勿施于人 (Do not impose on others what you yourself do not want), and the
《礼记》 warns
君子不强人以其所不能 (A gentleman does not press others beyond their ability). The four-character form
不强人所难 crystallized in later usage as a standard polite formula.