This passage comes from the Fifteenth Chapter of The Analects, "Duke Ling of Wei": "The Master said, 'Clever words confound virtue. If one cannot endure small irritations, it will disrupt a great plan.'" Zhu Xi's Collected Commentaries on the Analects states: "What is meant by 'cannot endure small irritations' includes both the Benevolence of a woman and the courage of a commoner." He further explains: "The Benevolence of a woman cannot bear to withhold affection; the courage of a commoner cannot bear to restrain anger—both can disrupt a great plan." (Classified Conversations of Master Zhu, Volume 45) Modern scholar Yang Shuda distinguishes three meanings of "cannot endure small irritations": "inability to endure anger"; "kind-heartedness that cannot bear to be harsh, unable to sever kindness with Yi (Righteousness)"; "stinginess that cannot bear to part with wealth" (Annotations on The Analects).
Confucius believed that enduring the "small" was for the sake of accomplishing great things. The "small" here refers to restraining personal resentment and greed for petty gains, as well as tolerating disrespectful behavior from others. If everyone can practice this forbearance, interpersonal conflicts can be eased, and relationships will naturally become harmonious.