Pesachim 6A

היינו דאיצטריך ״לא ימצא״. אלא למאן דאמר כממון דמי ⁠— ״לא ימצא״ למה לי? איצטריך, סלקא דעתך אמינא: הואיל וכי איתיה הדר בעיניה ⁠— לאו ברשותיה קאי, קמשמע לן.

That is the reason that it is necessary for the Torah to write: It should not be found, to indicate that there is a halakha unique to leaven. In this case, it is considered as though it were in his possession. However, according to the one who said: The legal status of an object that effects monetary loss is like that of money, why do I need the phrase: It should not be found? Obviously, the leaven is prohibited, as it is considered his property. The Talmud answers: It is nonetheless necessary, as it could enter your mind to say: Since when the leaven is intact it returns to the non-Jew in its pure, unadulterated form, it retroactively did not stand in the Jew’s possession and the Jew did not violate the prohibition against having leaven found on his property. Therefore, the verse teaches us that it is considered as though the leaven belonged to the Jew.

בעו מיניה מרבא: בהמת ארנונא חייבת בבכורה, או אין חייבת בבכורה? כל היכא דמצי מסלק ליה בזוזי ⁠— לא קא מיבעיא לן דחייב.

They raised a dilemma before Rava: Is the owner of an animal born into a herd from which the royal tax [arnona] is collected obligated in the mitzva to give the firstborn animal to a priest, as the animal still belongs to a Jew? Or perhaps he is not obligated to give the firstborn animal to the priest, as the obligation does not take effect on an animal partly owned by a non-Jew. The Talmud elaborates on the parameters of raising the dilemma: In any case where the Jew could dismiss the non-Jew tax collector with money in lieu of the animals, we do not raise the dilemma, as he is clearly obligated in the mitzva of the firstborn. The authorities own no part of the animal; the Jew merely owes them a monetary debt. Therefore, the animal is the property of the Jew exclusively.