Makkot 12B

רבי יהודה אומר: במערה ⁠– הלך אחר פתחה, באילן ⁠– הלך אחר נופו.

R' Yehuda says: With regard to a cave, follow its entrance; if the entrance is inside the city, the status of the entire cave is that of part of the city, and one may partake of tithes in it. With regard to a tree, follow its boughs. The baraita that states that with regard to second tithe in Jerusalem and cities of refuge one follows the boughs is in accordance with the opinion of R' Yehuda.

אימור דשמעת ליה לרבי יהודה גבי מעשר לחומרא, עיקרו בחוץ ונופו בפנים, כי היכי דבנופו לא מצי פריק ⁠– בעיקרו נמי לא מצי פריק. עיקרו מבפנים ונופו מבחוץ, כי היכי דבנופו לא מצי אכיל בלא פדייה ⁠– בעיקרו נמי לא מצי אכיל בלא פדייה.

The Talmud rejects that explanation. Say that you heard R' Yehuda express this opinion with regard to second-tithe produce in a situation where his ruling is a stringency, as in the case where the trunk of a tree is outside Jerusalem and its boughs are inside Jerusalem, just as among its boughs, one may not redeem second-tithe produce, and he must partake of it in Jerusalem, so too at its trunk he may not redeem second-tithe produce, even though it stands outside of Jerusalem. So too in a case where the trunk of a tree is inside and its boughs outside, there is a stringency: Just as among its boughs, one may not partake of second-tithe produce without redemption, so too at its trunk he may not partake of second-tithe produce without redemption, even though it stands inside Jerusalem.

אלא גבי ערי מקלט, בשלמא עיקרו בחוץ ונופו בפנים, כי היכי דבנופו לא מצי קטיל ליה, בעיקרו נמי לא מצי קטיל ליה. אלא עיקרו בפנים ונופו בחוץ, כי היכי דבנופו מצי קטיל ליה, בעיקרו נמי מצי קטיל ליה?! הא גואי קאי!

But with regard to cities of refuge, it may be otherwise: Granted, if its trunk is outside the boundary and its boughs are inside, just as among its boughs, the blood redeemer may not kill the unintentional murderer, so too at its trunk, he may not kill him. But if its trunk was inside and its boughs outside, would one say that just as among its boughs, the blood redeemer may kill him, at its trunk, he may also kill him? Isn’t the unintentional murderer standing inside the city of refuge? How could one say that it is permitted for the blood redeemer to kill him inside the city?