鍥而不舍 (鍥而不捨) qiè ér bù shě

qiè ér bù shě set phrase to carve away at something and not abandon it; to keep on working away at something
Domain: Idiom 成语
Notes: (CC-CEDICT '鍥而不捨'; CCI '鍥而不舍', pp. 105-106; Guoyu '鍥而不捨')