Reference for Keritot 4:1
סָפֵק אָכַל חֵלֶב, סָפֵק לֹא אָכַל. וַאֲפִלּוּ אָכַל, סָפֵק יֵשׁ בּוֹ כַשִּׁעוּר, סָפֵק שֶׁאֵין בּוֹ. חֵלֶב וְשֻׁמָּן לְפָנָיו, אָכַל אֶת אַחַד מֵהֶן וְאֵין יָדוּעַ אֵיזוֹ מֵהֶן אָכַל. אִשְׁתּוֹ וַאֲחוֹתוֹ עִמּוֹ בַבַּיִת, שָׁגַג בְּאַחַת מֵהֶן וְאֵין יָדוּעַ בְּאֵיזוֹ מֵהֶן שָׁגָג. שַׁבָּת וְיוֹם חֹל, וְעָשָׂה מְלָאכָה בְאַחַת מֵהֶן וְאֵין יָדוּעַ בְּאֵיזוֹ מֵהֶן עָשָׂה. מֵבִיא אָשָׁם תָּלוּי:
[If] one was in doubt whether he ate forbidden fat or not; [or] even [if] one was in doubt whether he ate the minimum amount [in a case where he certainly] did eat; [or if there were] permitted fat and forbidden fat before him, and he ate one of them and does not know which of them he ate; [or if] his wife and his sister were with him in the house and he unthinkingly [had relations] with one of them and does not know with which of them he unthinkingly [had relations]; or if he performed a <i>Melakhah</i> [a constructive activity forbidden on Shabbat and festivals] and does not know whether he did it on Shabbat or a weekday; he brings an <i>Asham Talui</i> [a guilt-offering brought upon possible commission of a sin].