I’m learning Siman 153 and I’m trying to figure out if there’s Hezek Re’iya if I spy on my neighbor in a way I know 100% Yediah Berura that there is no way he will ever know I’m spying on him therefore he will still feel completely comfortable to do everything private and i won’t be Mima’et his usage of his property at all. Any Mareh Mekomos you can give me would be greatly appreciated.
Even if he will never know, it is forbidden to spy or pry into another’s property.
According to the Ramban, a person does not acquire a chazakah on opening a window to another’s property (this is disputed by Rishonim).
One reason given for this by the Ramban (of which there is no dispute; the dispute is only concerning the chazakah) is because of a concrete prohibition again actually looking into the other’s property and invading his privacy.
Once the window is open, it is virtually impossible for a person living in the offending property to be wary of not looking into his neighbor’s home and invading his privacy. Therefore, we tell him: “Close up your window, and do not enter a constant state of sin” (Ramban on Bava Basra 59b).
The Rama (Bava Basra 3a) likewise writes that invading another’s privacy is an actual prohibition, derived from Bilam’s praise of Israel, and causes the Shechinah to depart from among Israel.
In a similar vein the Taz (Orach Chaim 637:4) rules that a person may not enter his fellow’s Sukkah in order to fulfill the mitzvah of Sukkah while the owner is there with his family. Even if there is general permission to enter the Sukkah, one cannot do so when this constitutes an actual invasion of privacy.
The Rema (154:7) cites this principle, explaining that even if one acquires a chazakah concerning opening the window itself, it remains forbidden to look inside another’s private domain, and the neighbor suffering from hezek reiyah can demand that his neighbor refrain from looking. One must likewise refrain from looking into somebody’s house, even through an open window (Pischei Choshen, Nezikin, Chap. 14 note 3).