Yiddish: It's a mitzvah to tickle a widow.

SOURCE: Bernstein, Jüdische Sprichwörter und Redensarten, Erotica und Rustica. The following may be added:

... in front or in back.  |  ... fun fornt oder fun hintn.  |  .פֿון פֿאָרנט אָדער פֿון הינטן ...

A mitzvah can be thought of as a good deed.  More precisely, it is a commandment or the fulfillment of a commandment.  Variation:

A yesoyme iz a mitsve tsu kitslen.  |  .אַ יתומה איז אַ מיצװה צו קיצלען
It's a mitzvah to tickle an orphan.

SOURCE: Stutchkoff, Der Oytser fun der Yidisher Shprakh

אַן אַלמנה איז אַ מיצװה צו קיצלען.

An almone iz a mitsve tsu kitslen.

It's a mitzvah to tickle a widow.