Mishnayos Kerisos Perek 5 Mishnah 7

If one had a piece of forbidden fat and a piece of sacrificial forbidden fat and he ate one of them and does not know which of them he ate, he brings a sin offering as he certainly ate forbidden fat. Rabbi Akiva says: He also brings a provisional guilt offering, as perhaps he ate the sacrificial fat, in accordance with his opinion that one brings a provisional guilt offering even in the case of uncertainty with regard to misuse of consecrated property. If he then ate the second piece, he brings two sin offerings, as he ate two pieces of forbidden fat, and a definite guilt offering for misuse of consecrated property. If one person ate the first piece and another person came and ate the second piece, this person brings a sin offering and that person brings a sin offering. Rabbi Akiva says: This person and that person each bring a provisional guilt offering as well, due to the uncertainty as to which of them ate the sacrificial fat. Rabbi Shimon says: This person brings a sin offering and that person brings a sin offering and both of them bring one guilt offering as partners, and they stipulate that the offering should be credited to the one who ate the sacrificial fat. Rabbi Yosei says: The two of them do not bring one guilt offering.

חֲתִיכָה שֶׁל חֵלֶב וַחֲתִיכָה שֶׁל חֵלֶב קֹדֶשׁ, אָכַל אֶת אַחַת מֵהֶן וְאֵין יָדוּעַ אֵיזוֹ מֵהֶן אָכַל, מֵבִיא חַטָּאת. רַבִּי עֲקִיבָא אוֹמֵר, מֵבִיא אָשָׁם תָּלוּי. אָכַל אֶת הַשְּׁנִיָּה, מֵבִיא שְׁתֵּי חַטָּאוֹת וְאָשָׁם וַדָּאי. אָכַל אֶחָד אֶת הָרִאשׁוֹנָה וּבָא אַחֵר וְאָכַל אֶת הַשְּׁנִיָּה, זֶה מֵבִיא חַטָּאת וְזֶה מֵבִיא חַטָּאת. רַבִּי עֲקִיבָא אוֹמֵר, זֶה מֵבִיא אָשָׁם תָּלוּי וְזֶה מֵבִיא אָשָׁם תָּלוּי. רַבִּי שִׁמְעוֹן אוֹמֵר, זֶה חַטָּאת וְזֶה חַטָּאת, וּשְׁנֵיהֶם מְבִיאִים אָשָׁם אֶחָד. רַבִּי יוֹסֵי אוֹמֵר, אֵין שְׁנַיִם מְבִיאִין אָשָׁם אֶחָד: