Positive commandment · Mitzvat Aseh #69 of 613
A sin-offering for an individual who sinned inadvertently in a commandment for which we are liable excision
להקריב היחיד קרבן חטאת אם שגג במצות לא תעשה שחייבים עליה כרת
The verse · Vayikra 5:1
וְנֶפֶשׁ כִּי־תֶחֱטָא וְשָׁמְעָה קוֹל אָלָה וְהוּא עֵד אוֹ רָאָה אוֹ יָדָע אִם־לוֹא יַגִּיד וְנָשָׂא עֲוֺנוֹ
“And if a person sin, and hear the voice of adjuration, and is a witness, whether he has seen or known of it; if he do not utter it, then he shall bear his iniquity.”
The Rambam’s words
For each individual to offer a sin offering if he unintentionally violates a negative commandment punishable by karet, as [Leviticus 5:1] states: "When a person sins...." it appears to be an error, for the passage it introduces deals with the adjustable guilt offering (Positive Mitzvah 72). The verse which introduces the laws of the sin offerings is Leviticus 4:27: "If one person sins...."
להקריב היחיד קרבן חטאת אם שגג במצות לא תעשה שחייבים עליה כרת, שנאמר: "וְנֶפֶשׁ כִּי תֶחֱטָא" (ויקרא ה, א).
Who & when
“And [it] is practiced at the time of the [Temple] by males and females.”
Where in the Mishneh Torah
Hilchot Offerings for Unintentional Transgressions הלכות שגגות