It's a worthy accomplishment to extract even the smallest charity from a miser. SOURCE: Bernstein, Jüdische Sprichwörter und Redensarten. A mitzvah can be thought of as a good deed; more precisely, it is a commandment or the fulfillment of a commandment. Compare:
Even a hair from a pig is good. | Fun a khazer a hor iz oykh gut. | .פֿון אַ חזיר אַ האָר איז אויך גוט
SOURCE: Stutchkoff, Der Oytser fun der Yidisher Shprakh