Our Gemara on Amud Aleph quotes Devarim (12:17):

You may not (lo suchal) eat within your gates the tithe of your grain.

The Hebrew lo suchal literally translates as “you cannot,” not “you may not.” How can it say “you cannot” when one is physically able to do so, despite the prohibition?

Kesav Vehakabbalah explains that prior strong admonitions make the taboo so intense that it feels like one cannot violate it. Stories of Gedolim reflect this. It’s said that Rav Moshe, when he saw a boy davening Shemoneh Esreh blocking his path, stood still as if facing a brick wall (per Shulchan Aruch O.C. 102:4, though a difficult law to commonly adhere to.) Similarly, a friend recounted that Rav Gustman ZT”L, walking to shul early Shabbos morning in Jerusalem, refused to cross a street against a red “do not walk” sign, despite no cars being present (given the time and place), as if it were physically impossible.

Tiferes Shlomo (R’eh) offers another view. Certain holiness, like eating maaser in Jerusalem or at a tzaddik’s table, cannot be replicated elsewhere. The verse emphasizes that you cannot eat maaser as maaser outside its designated context.

Thus, the text’s provocative language conveys two messages: either a state where violating Torah is unthinkable, akin to impossibility, or a recognition that what seems possible is hollow without its proper spiritual context.