Reference for Bava Batra 197:9
<big><strong>גמ׳</strong></big> פותחת להיכא אמר ר' יוחנן שניהם לבור בשלמא בעל הבור בעי לאשתמורי מיא דבוריה אלא בעל הבית למה ליה א"ר אלעזר
and their faces were turned sideways as a student who takes leave of his master.<span class="x" onmousemove="('comment',' A student, on taking leave of his master, turns sideways for some distance, before turning his back completely on him. ');"><sup>24</sup></span> <b><i>MISHNAH</i></b>. HE WHO OWNS A CISTERN WITHIN ANOTHER MAN'S HOUSE, GOES IN WHEN IT IS USUAL FOR PEOPLE TO GO IN, AND GOES OUT WHEN IT IS USUAL FOR PEOPLE TO GO OUT. HE MUST NOT BRING IN HIS BEAST [THROUGH THE OTHER'S HOUSE] TO GIVE IT DRINK FROM HIS CISTERN. BUT MUST FILL [HIS VESSEL] AND GIVE [THE BEAST] TO DRINK OUTSIDE. ONE OF THEM MAY MAKE FOR HIMSELF A LOCK, AND THE OTHER MAY [ALSO] MAKE FOR HIMSELF A LOCK. <b><i>GEMARA</i></b>. Where [is] the lock [to be attached]? — R. Johanan said: Both<span class="x" onmousemove="('comment',' The lock of the owner of the cistern and that of the owner of the house. ');"><sup>25</sup></span> to the cistern. This is right [in the case of] the owner of the cistern, [for] he has to protect the water of his cistern; but for what purpose does the owner of the house [require a lock]? — R. Eleazar said: