Musar zu Schemot 13:3

"Remember what the L-rd your G-d did to Miriam" — "Mention it with your mouth always" [Ramban]. And he writes there that this is an explicit positive commandment, just as (Shemoth 20:8): "Remember the day of Sabbath to sanctify it," (Ibid. 13:3): "Remember this day that you went out of Egypt, etc." And this, too, just as the former, is a positive commandment, to mention the great punishment that the L-rd brought upon the tzadeketh, the prophetess, who spoke only of her brother, the "redeemed of her soul," whom she loved as her soul, and who did not speak thus to his face, to embarrass him, and not in public, but only in private, to her holy brother [Aaron] — and all of this did not avail [to save her from leprosy.] You, too, if 'you sit and speak against your brother; if you slander your mother's son,' (Psalms 50:20), you will not be saved."