Perception must be guarded by yiras Shomayim

נסמך ויקח קרח לפרשת ציצית שלמעלה.

"Vayikach Korach" (And Korach took) is placed adjacent to the parsha of tzitzis that precedes it.

The Sefas Emes opens by noting the deliberate juxtaposition: the parsha of Korach's rebellion immediately follows the mitzvah of tzitzis at the end of the previous parsha, and this ordering carries a lesson.

דאיתא עינו הטעתו.

For it is taught: "his eye misled him."

Chazal say that Korach's downfall came because his "eye" deceived him — through a flawed way of seeing, he was led to a false conclusion that justified his rebellion.

ובשם הרב הק' מלובלין אמרו להוכיח מכאן כי גם רוח הקודש יכול להזיק לאדם שאינו שומר עצמו כראוי.

And in the name of the holy Rav of Lublin they said, to prove from here that even ruach hakodesh (divine inspiration) can harm a person who does not guard himself properly.

The Rebbe of Lublin learns from Korach that even a lofty spiritual gift like ruach hakodesh is not automatically protective; without proper yiras Shomayim and self-watchfulness, even such an elevated perception can become a snare. Korach did sense something true, but lacking the proper safeguards, that very perception led him astray.

כי מצות ציצית על שם הסתכלות כמ"ש רש"י ובודאי המצוה מפקח עיני האדם ולכן כתיב מיד ולא תתורו אחרי לבבכם ואחרי עיניכם ב' לבבות וב' עינים כמ"ש בפרשה הקודמת וקרח לקח לו ביותר זה ההסתכלות ונכשל בו:

For the mitzvah of tzitzis is bound up with seeing, as Rashi writes, and certainly the mitzvah opens a person's eyes; and therefore it is written immediately afterward, "Velo sasuru acharei levavchem v'acharei eineichem" (And you shall not stray after your heart and after your eyes) — two hearts and two eyes, as is explained in the previous parsha — and Korach seized this faculty of seeing excessively, and through it he stumbled.

Tzitzis is called the mitzvah of "seeing" ("ur'isem oso" — and you shall see it), and its purpose is to refine and illuminate a person's vision so that it leads upward to Hashem. Precisely because seeing has such power, the Torah immediately warns "velo sasuru" — do not let the eye wander after the desires of the heart, for there are two hearts (a good inclination and a yetzer hara) and two ways of seeing (one that elevates and one that misleads). Korach grasped at this power of perception in an unbalanced, ungoverned way — taking the heightened sight without the bittul and self-restraint that must accompany it — and so the very gift of vision became the instrument of his stumbling.

Summary: The placement of Korach's rebellion right after the mitzvah of tzitzis teaches that spiritual perception is a double-edged power. Tzitzis sharpens a person's vision so it leads to Hashem, and the warning "velo sasuru acharei eineichem" follows immediately because heightened sight, when not guarded by yiras Shomayim and bittul, can mislead. Korach — and even one given ruach hakodesh, per the Rav of Lublin — can be harmed by his own elevated perception when he fails to watch himself, and that is how "his eye misled him."