A few quotes from the Rabbi on 'Tzedakah and Healing'
in which he teaches the obligation to eulogize charitable people as a Torah scholar's obligation
The deceased was a charitable individual. When people went to fulfill the obligation of gathering money for charity, he was often the first to give. We are all therefore obligated to eulogize him, even those who did not directly benefit from him. Measure for measure; just as he was a benefactor for other people, and his death put an end to the benefit and value they received, thus must other people come to his benefit and eulogize him. This is the reason the sages said that "The Holy One, blessed be He, will in the future prepare a canopy and shelter for those who fulfill the mitzvah of charity with those who toil at Torah. "For to be in the shelter of wisdom is to be also in the shelter of money". Just as the toil of some at Torah benefits others, so do those who fulfill the commandment of charity benefit others; just as Torah scholars are to be eulogized, so are those who fulfill the mitzvah of charity to be eulogized.
Divrei Yosef, Sermons on the Torah and on Festivals, Sermons for Eulogies, p. 140, Private publication of the author's manuscripts, Jerusalem 2010