Reference for Pesachim 125:4

וקסבר ר' מאיר לא בעינן פיו ולבו שוין ורמינהו המתכוין לומר תרומה ואמר מעשר מעשר ואמר תרומה או שאיני נכנס לבית זה ואמר לזה שאיני נהנה לזה ואמר לזה לא אמר כלום עד שיהו פיו ולבו שוין

This proves that the view that the first statement only is regarded is maintained even in respect of halves, for the sacrifice is large enough to permit us to assume that each wrongful intention was expressed with respect to a different part thereof, and yet R'Judah disagrees. To this Abaye answered, Do not think that the slaughtering counts only when it is completed, so that the two intentions come together at the same moment. On the contrary, the slaughtering counts from beginning to end, and in the passage quoted he cut one organ of the animal with the intention of eating it after time, and the second organ with the intention of eating it without the permitted area, R'Meir holding that you can make an animal piggul even at one organ only.

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