The most influential late-Qīng kǎozhèng (textual-evidential) scholar, philologist, and lay-Buddhist commentator. Zì Yìnfǔ 蔭甫, sobriquets Qǔyuán jūshì 曲園居士 / Qǔyuán lǎorén 曲園老人. Lifedates 1821-12-25 (清道光元年十二月初二) – 1907-02-05 (光緒三十二年十二月二十三), age 86. Native of Déqīng 德清 (Zhèjiāng); usually styled Déqīng Yú Yuè 德清俞樾.
Jìnshì 1850; protégé of Zēng Guófān 曾國藩. Long-tenured director of the Gūjīng jīngshè 詁經精舍 academy at Hángzhōu (1868–1898; thirty-one years). Teacher of Zhāng Bǐnglín 章炳麟 (Tàiyán) and others — i.e., the scholastic father of the late-Qīng / Republican-era national-studies movement. Vast literary corpus collected as the Chūnzàitáng quánshū 春在堂全書. Defining works include the Qúnjīng píngyì 群經平議 (parallel to Wáng Niànsūn’s Jīngyì shùwén), the Zhūzǐ píngyì 諸子平議, the Gǔshū yíyí jǔlì 古書疑義舉例, and many others.
Two Vajracchedikā commentaries in the Xùzàngjīng: the two-juan Jīngāng jīng zhù 金剛經注 (KR6c0094, X25 no. 506), composed 光緒九年十月 = November 1883 at Wújiāng on a boat; and the one-juan Jīngāng jīng dìngyì 金剛經訂義 (KR6c0095, X25 no. 507), a kǎozhèng-style critical-philological notebook on disputed readings of the sūtra. Yú’s Vajracchedikā commentaries are the rare instance of a major late-Qīng textual-critic applying kǎozhèng method directly to a Mahāyāna sūtra.
Standard biographies: Qīngshǐ gǎo j. 482; modern monographs by Zhāng Sānxī 張三夕 and others.