Natural Pull Toward Good
העדותי בכם כו' פירש"י ז"ל כלום שינו שמים וארץ מידתם כו'
On the verse "I have called as witnesses against you..." (Devarim 30:19), Rashi z"l explains: Have the heavens and the earth ever changed their nature? — Just as the sun and moon never deviate from the path set for them, so too you should not deviate from following the Torah.
The verse calls heaven and earth as witnesses, and Rashi teaches that just as they never abandon the order Hashem set for them, Bnei Yisrael too should remain faithful to the Torah.
ולכאורה מאי ראי' מהם שאין להם בחירה
At first glance, what proof is there from the heavens and the earth, seeing that they have no free choice, whereas man does?
The Sfas Emes raises an obvious question: heaven and earth have no free will, so how can their constancy serve as a lesson for man, who does have free will?
אך עכ"פ מובן כי מדרך הטבע להיות נמשך כל דבר אחר הש"י וציויו
Yet in any case we learn from them this much: it is the very way of nature for every created thing to be drawn after Hashem and His command.
His answer begins by noting that nature itself shows that every creation is naturally pulled toward Hashem and His command.
א"כ וודאי לא נגרע האדם מזה רק שניתן לו בחירה יצ"ט ויצה"ר
If so, surely man is not lacking in this regard either; the only difference is that man was given free choice — a yetzer tov and a yetzer hara.
Man shares this same natural pull; the only thing added to man is the gift of free choice, with both a yetzer tov and a yetzer hara.
ואם לא יגבור הרע על הטוב ממילא מצד עצמו ימשך אחר הטוב ככל הנבראים
And if the evil does not overpower the good, then of his own accord man will be drawn after the good, just like all the rest of creation.
Therefore, if a person simply does not let his yetzer hara win, his built-in nature will carry him toward the good on its own, exactly like the rest of creation.
ומזה מובן ולך ה' החסד כו' תשלם לאיש כמעשהו
From this we can understand the verse "And Yours, Hashem, is kindness, for You repay each man according to his deeds" (Tehillim 62:13).
This sheds light on the verse that calls it kindness when Hashem rewards a person according to his deeds.
וקשה מה החסד כדכ' בגמ'
But this is difficult, for what kindness is there in this, as the Gemara asks?
The difficulty, raised in the Gemara, is why this should be called kindness at all — surely reward for one's deeds is simple justice, not a favor.
אך גם מי שעושה טוב הוא מהש"י ורק שהוא נקי ולא נמשך אחר היצה"ר ממילא נתעורר הפנימיות שנתן הש"י באדם לטוב כנ"ל
The answer is that even when a person does good, the good itself comes from Hashem; man's only part is that he stays clean and does not allow himself to be drawn after the yetzer hara, and then automatically the inner core of goodness that Hashem placed within man is awakened, as explained above.
The resolution is that the good a person does is really Hashem's doing; the person only keeps himself clean of the yetzer hara, and then the inner goodness Hashem implanted in him awakens by itself.
וא"כ הכל רק חסד הש"י:
If so, then everything is purely the kindness of Hashem.
Since even our good deeds flow from Hashem, the reward we receive is entirely an undeserved kindness.
Summary: The Sfas Emes addresses Rashi's teaching that the unchanging constancy of heaven and earth is a model for Bnei Yisrael's faithfulness to the Torah, and asks how lifeless creations without free choice can serve as a lesson for man. He answers that the natural drive of all creation to follow Hashem and His command exists in man as well; the only difference is that man was granted free choice, a yetzer tov and a yetzer hara. As long as a person does not let the evil overpower the good, his own inner nature will draw him toward the good just like the rest of creation. On this basis he resolves the Gemara's difficulty on the verse "And Yours, Hashem, is kindness, for You repay each man according to his deeds": since even the good a person does flows from the inner goodness Hashem placed within him, and his only task is to stay clean of the yetzer hara, the reward is entirely Hashem's kindness.