Mishneh Torah — Positive Mitzvot מצוות עשה, Chapter 70

להקריב היחיד קרבן אם נסתפק לו אם חטא חטא שחייבים עליו חטאת או לא חטא, שנאמר: "וְלֹא יָדַע וְאָשֵׁם וְהֵבִיא אֶת אֲשָׁמוֹ" (ויקרא ה, יז) וזה הוא נקרא אשם תלוי.

For an individual to offer a sacrifice if he is in doubt whether or not he transgressed a prohibition for which he would be liable for a sin offering, as [Leviticus 5:17-18] states: "If he does not know, he still bears responsibility...and he shall bring his guilt offering." This is referred to as "the conditional guilt offering."