Burning away the intrusive thought in avodah

זאת תורת העולה היא העולה.

"This is the law of the olah (burnt-offering): it is the olah" (Vayikra 6:2).

The Sefas Emes notes the seemingly redundant phrasing "it is the olah," which invites a deeper reading.

בזוה"ק היא העולה מחשבה רעה כו'.

In the Zohar HaKadosh: "it is the olah" refers to an evil thought that "rises up," etc.

The Zohar reads "ha'olah" (that which rises) as alluding to a stray, evil thought that ascends in a person's mind.

פי' שמיד שיש תורת העולה יש גם כן מחשבה זו לעומת זה.

The meaning is that as soon as there is the "law of the olah," there is also this thought, "this corresponding to that."

Wherever there is an avodah of elevation (the olah), the yetzer hara sends a corresponding intrusive thought to oppose it — zeh l'umas zeh.

והטעם על מוקדה שעי"ז מוצא מקום זאת המחשבה לעשותה אפר ע"י שמתבטלה ברוב התלהבות אמת שבלב העובד ה'.

And this is the reason for "on its flame" (al mokdah) — for through this the place is found to turn this thought into ash, in that it is nullified within the great, true fervor in the heart of the one who serves Hashem.

The fire on the altar represents the burning hislahavus (fervor) of avodas Hashem; the intrusive thought is consumed and nullified in that genuine inner flame, reduced to ash.

והרמז תרומת הדשן שנבלעת במקומה.

And the hint is in terumas hadeshen (the removal of the ashes), which is absorbed in its place.

The mitzvah of gathering the ashes — which were miraculously absorbed into the ground beside the altar — alludes to the fate of that nullified thought.

ושמו אצל המזבח.

"And he shall place it beside the altar" (Vayikra 6:3).

The ash is set down beside the altar rather than discarded entirely — a deliberate placement that the Sefas Emes will explain.

להראות כי נמצא למחשבה זרה ג"כ מקום אחר השריפה שנעשית אפר כנ"ל:

To show that even for the foreign thought there is found a place after the "burning," once it has become ash, as above.

Even the alien thought, once burned up in the fire of true avodah and reduced to ash, is not wasted — it too finds a rightful place, its energy redeemed and elevated.

Summary: The Zohar reads "it is the olah" as the evil thought that rises against a person precisely when he engages in the avodah of elevation (zeh l'umas zeh). The remedy is the fire of the altar — the burning, true fervor of avodas Hashem — which consumes and nullifies the intrusive thought into "ash." And like the terumas hadeshen absorbed beside the altar, even that nullified foreign thought ultimately finds its rightful, redeemed place.