Yirah and the mitzvos of the heart

ברש"י דבר המסור ללבו של אדם נאמר בו ויראת מאלקיך.

Rashi explains: regarding a matter that is entrusted to a person's heart, the Torah says, "and you shall fear your God."

The Sefas Emes cites Rashi's rule that wherever an action depends on a person's inner intent — something only he and Hashem can know — the Torah attaches the phrase "and you shall fear your God," invoking yiras Shomayim as the safeguard.

פשוט שע"י היראה יכולין לקיים דבורים המסורים ללב.

It is straightforward that through yirah (fear of Hashem) one is able to fulfill those matters that are entrusted to the heart.

The simple reading: only yiras Shomayim guarantees that a person will be honest in those mitzvos where no outside observer can hold him accountable.

אמנם ג"כ י"ל שאלה המצות התלוין בלב ע"י שמקיימין אותן זוכין ליראה.

However, one may also explain the reverse: that through fulfilling these mitzvos which depend on the heart, one merits to attain yirah.

He now turns the causation around — keeping these inner mitzvos is itself what earns a person yiras Shomayim, rather than yirah merely being their precondition.

כי כל מצוה במעשה מתקן מעשה האדם.

For every mitzvah performed in action repairs a person's deeds.

A physical mitzvah does its tikkun (rectification) on the realm of action, refining the way a person behaves in the world.

וכמו כן מצות התלוין במחשבת לב האדם מתקנין לבו של האדם.

And likewise, mitzvos that depend on the thought of a person's heart rectify the heart of the person.

By the same logic, mitzvos of the heart work their tikkun on the heart itself — and since yirah resides in the heart, fulfilling them purifies and builds that very faculty.

וכן שמעתי מפ"ק אא"ז מו"ר ז"ל ע"פ ולא תונו כו' את עמיתו ויראת מאלהיך כו' שע"י שמירת אונאת דברים זוכין ליראה.

And so I heard from the holy mouth of my grandfather and teacher, of blessed memory, on the verse "You shall not wrong… one another, and you shall fear your God" — that through guarding oneself from ona'as devarim (wronging another with words) one merits yirah.

He brings his grandfather (the Chiddushei HaRim) as support: the prohibition of hurtful speech is precisely such a heart-dependent mitzvah, and keeping it is what brings a person to yiras Shomayim.

ובאמת ב' הפירושים אמת ע"פ מ"ש שכר מצוה מצוה.

And in truth both explanations are correct, in line with what is said: "the reward of a mitzvah is a mitzvah."

He reconciles the two readings through the teaching of Avos (4:2): the reward for one mitzvah is the ability to do the next — so yirah and the heart-mitzvos feed each other in a cycle.

ובוודאי ע"י עומק היראה יכולין לקיים יותר מצות התלוין בלב לכן שכר המצוה היראה כדי לקיים עי"ז המצוה בטוב יותר וכן לעולם:

And certainly, through the depth of yirah one is able to fulfill more of the mitzvos that depend on the heart; therefore the reward of the mitzvah is yirah, so that through it one may fulfill the mitzvah even better — and so it continues forever.

The two explanations are one continuous spiral: keeping a heart-mitzvah grants deeper yirah, and that deeper yirah enables one to keep the mitzvah better still, ascending without end.

Summary: Rashi attaches "you shall fear your God" to mitzvos entrusted to the heart. The Sefas Emes shows this works in both directions — yirah enables one to keep these inner mitzvos, and keeping them in turn earns deeper yirah. By the principle that "the reward of a mitzvah is a mitzvah," the two form an ever-rising cycle of avodah.