Mishnah Taharos 4:12: The uncertainty [regarding the purity status] of non-sanctified foods, this is the purity of abstention [i.e. of those who are careful to eat in purity even non-sanctified foods; and such foods, when their status is uncertain, are pure]. The uncertainty regarding [something which may or may not have been rendered impure by] vermin, [its status is] in accordance with how they were found [i.e. if the item in question was not actually touching the vermin when it was found, it is assumed to be pure]. The uncertainty of blights [i.e. regarding the purity status of someone that may have been rendered impure by someone impure due to an illness, such as leprosy], at the beginning he is pure until he is determined [by the priest] as impure; once he has been determined impure, his uncertainty [i.e. a case of someone or something which may or may not have been rendered impure by him] is impure. The uncertainty regarding [one's] status as a Nazirite [i.e. if someone took a vow to be a Naziritecontingent on something which remains uncertain], he is permitted [to do the things a Nazirite is forbidden from doing, i.e. he is not a Nazirite]. The uncertainty regarding [the status of] a first born, whether first born humans or first born animals, whether pure or impure [i.e. kosher or non-kosher], the burden of proof is upon the one [who wants] to remove [possessions] from his fellow [i.e. the priest who makes a claim on the first born must demonstrate that it is a first born before he can take it].

סְפֵק הַחֻלִּין, זוֹ טָהֳרַת פְּרִישׁוּת. סְפֵק שְׁרָצִים, כִּשְׁעַת מְצִיאָתָן. סְפֵק נְגָעִים, בַּתְּחִלָּה טָהוֹר, עַד שֶׁלֹּא נִזְקַק לַטֻּמְאָה. מִשֶּׁנִּזְקַק לַטֻּמְאָה, סְפֵקוֹ טָמֵא. סְפֵק נְזִירוּת, מֻתָּר. סְפֵק בְּכוֹרוֹת, אֶחָד בְּכוֹרֵי אָדָם וְאֶחָד בְּכוֹרֵי בְהֵמָה, בֵּין טְמֵאָה בֵּין טְהוֹרָה, שֶׁהַמּוֹצִיא מֵחֲבֵרוֹ עָלָיו הָרְאָיָה:

Mishnah Taharos 4:13: The uncertainty regarding [one's obligation to bring] sacrifices, [for example]: a woman who has upon her five uncertain [obligations to bring the sacrifice brought after] births [i.e. if she miscarried and is uncertain whether it was a birth obligating her to bring a sacrifice], or five uncertain discharges [i.e. she is uncertain if they were discharges obligating her to bring a sacrifice]; she brings one sacrifice, and can then eat from the offering, and she does not have an obligation to bring the rest [of the sacrifices].

סְפֵק קָרְבָּנוֹת, הָאִשָּׁה שֶׁיֵּשׁ עָלֶיהָ סְפֵק חָמֵשׁ לֵידוֹת וּסְפֵק חָמֵשׁ זִיבוֹת, מְבִיאָה קָרְבָּן אֶחָד, וְאוֹכֶלֶת בַּזְּבָחִים, וְאֵין הַשְּׁאָר עָלֶיהָ חוֹבָה: