Inherited Merit Of Teshuvah
ומל ה"א את לבבך וא"ל זרעך
"And Hashem your God will circumcise your heart and the heart of your offspring" (Devarim 30:6).
The Sfas Emes opens with the pasuk that promises Hashem will Himself remove the spiritual blockage of the heart, both for a person and for his children.
פי' כי השב בתשובה יזכה גם לזרעיו אחריו להסיר ערלת לבבם
The meaning is that one who returns in teshuvah merits that even his offspring after him will have the foreskin of their hearts removed.
He explains that the power of teshuvah reaches beyond the individual: when a person does genuine teshuvah, he draws down the merit so that his descendants too can have their hearts opened to serve Hashem.
והקדמונים נתנו רמז בפסוק זה א"ל ואת לבב ר"ת אלול הוא כנ"ל
The early ones gave a hint in this verse: the words 'God' (Aleph-Lamed), 'and the heart' (Vav-Aleph-Lamed-Beis) — their first letters spell out 'Elul,' as explained above.
The earlier authorities found the month of Elul alluded to within this very pasuk, as the first letters of several of its words form the name 'Elul,' tying the verse to the season of teshuvah.
כי בזמן זה היו בנ"י בעלי תשובה בעת שקיבל מרע"ה לוחות שניות
For it was at this time that Bnei Yisrael were baalei teshuvah, masters of repentance, at the moment when Moshe Rabbeinu received the second Luchos.
He grounds this in the historical event of Elul: it was during these days that Bnei Yisrael stood as baalei teshuvah while Moshe Rabbeinu received the second set of Luchos after the cheit haEigel.
לכן אלו הימים הם ימי רצון גם לנו זרעם אחריהם בזכות התשובה שעשו אבותינו כנ"ל:
Therefore these days are days of ratzon, of Divine favor, even for us, their offspring after them, in the merit of the teshuvah that our forefathers performed, as explained above.
Because our forefathers achieved that teshuvah in Elul, the merit endures, making these same days a time of Divine favor for us, their descendants, as well.
Summary: The Sfas Emes expounds the pasuk that Hashem will circumcise the heart of a person and of his offspring after him, teaching that genuine teshuvah is not a private achievement but a merit that reaches one's children, removing the foreskin of their hearts as well. He cites the early authorities who found the name Elul hinted within this very verse through the first letters of its words. This hint is rooted in the events of Elul, when Bnei Yisrael stood as baalei teshuvah during the days that Moshe Rabbeinu received the second Luchos. Because of the teshuvah our forefathers accomplished then, these days remain days of ratzon, of Divine favor, for us, their offspring after them, in the merit of what the avos achieved.