纤尘不染 (纖塵不染) xiān chén bù rǎn

xiān chén bù rǎn set phrase untainted by even a small speck of dust; selfless and incorruptible
Domain: Idiom 成语
Notes: Same as 一尘不染 (CC-CEDICT '一塵不染'; Guoyu '纖塵不染')