Explanation：
To sacrifice oneself for a just cause.
Story：
In the Spring and Autumn Period there lived a martial hero named Yu Rang. When his patron， Zhi Bo， was killed by Zhao Xiangzi， Yu Rang swore to avenge him. Gaining employment as a servant in the household of Zhao Xiangzi， his identity was discovered before he had a chance to assassinate Zhao. His intended victim， however， was moved by Yu Rang's loyalty to his late master and set him free， despite Yu Rang's admission that he would still try to kill him.
舍生取義
解釋：
為正義事業而犧牲生命。
故事：
春秋時，晉國有個勇士名叫豫讓，投靠在智伯門下，很受重用。後來，智伯被趙襄子殺害。豫讓躲了起來，下決心要為智伯報仇。過了幾個月，豫讓裝扮成仆役混進趙府，伺機刺殺趙襄子。結果在茅廁裏被發現，趙襄子見豫讓為主人報仇就放了他。豫讓說：“妳雖然放了我，但我還會刺殺妳的！”
Returning home， Yu Rang cut off his eyebrows and beard， and swallowed burning charcoal to hoarsen his throat， in order to escape recognition both in appearance and voice. Some of his friends suggested， "Would it not be easier if you pretended to switch allegiance to Zhao Xiangzi and then killed him when he was off his guard？" Indignantly， Yu Rang replied， " How could a righteous man do such a thing？"
One day Yu Rang hid under a bridge on a route that he knew Zhao Xiangxi was to take. But when the latter's carnage drew near the bridge the horses began to neigh in fear. A search soon found Yu Rang under the bridge， and he was hauled out by Zhao Xiangzi's men. Zhao said to him： "I admire your devotion to your late master， but this time I really cannot pardon you." Yu Rang replied， "I thank Your Excellency for your kindness. But I have one last request. Please take off your coat and let me thrust my sword through it three times， so that I can satisfy myself that I have avenged my ex-master. Then I can die contented." Zhao Xiangzi was touched by Yu Rang's sincerity， and took off his coat. Thereupon， Yu Rang thrust his sword through it three times before cutting his own throat.
豫讓回去後，剃去眉毛和胡子，又吞食熱炭，把聲音弄嘶啞，以便從形象到聲音都不讓人認出來。朋友們對他說：“妳如投靠趙襄子，得到他的信任後，再行刺他，不是更方便嗎？”豫讓回答說：“作為壹個勇士，怎麽可以做這樣不仁不義的事呢！”
這壹天，豫讓得知趙襄子外出辦事，他就預先埋伏在橋下，趙襄子來到橋邊，馬匹突然驚叫起來。趙襄子命人到處搜查，在橋下把豫讓抓了出來。趙襄子說：“妳舍生取義，確實令人尊敬。但這次我不能饒恕妳了！”豫讓說：“多謝趙公厚義，但我臨死前請求妳能把外袍脫下來，讓我刺三劍，償我為主復仇的意願。我死而無怨了。”趙襄子見他這樣忠誠，大為感動，便脫下外袍。豫讓刺了外袍之後，自刎而亡。 豫讓甘願舍棄生命，也要完成道義的行為，便成了“舍生取義”的成語。