Parashas Vayeishev · Passuk 37:22
And Reuven said unto them: Shed no blood; cast him into this pit that is in the wilderness, but lay no hand upon him — that he might deliver him out of their hand, to restore him to his father.
Torah Temimah points to Midrash Ruth Rabbah 5 (and parallel teachings on publicizing a mitzvah).
English: From here we learn that it is proper to write and publicize one who performs a mitzvah, for the Torah itself publicized the mitzvah of Reuven who intended to save Yosef and restore him to his father.
Derash on the verse (midrashic sugya) — not a formal named middah of the 13. The explicit statement of Reuven’s purpose is taken as a model for publicizing good deeds.
It is appropriate to record and make known the performance of a mitzvah. The Torah itself did so by revealing Reuven’s plan to save Yosef.