ובפרט כשיזכור טומאת נפשו בחטאת נעורים, והפגם שעשה בעליונים, ושם הוא למעלה מהזמן, וכאלו פגם ונטמא היום, חס ושלום, ממש
Especially so, if he calls to mind the contamination of his soul with the sin of youth, and the blemish he has wrought thereby in the supernal worlds —the source of his soul. The fact that they were sins of “youth”, belonging to a time and to a spiritual level from which he may presently be far removed, is irrelevant in these supernal worlds — where everything is timeless, and it is as if he had caused the blemish and defiled himself this very day, G‑d forbid.
ואף שכבר עשה תשובה נכונה, הרי עיקר התשובה בלב, והלב יש בו בחינות ומדרגות רבות, והכל לפי מה שהוא אדם, ולפי הזמן והמקום, כידוע ליודעים
True, he may already have repented sincerely and thereby removed the blemish and cleansed himself. But the essence of repentance is in the heart, and in the heart there are many distinctions and levels. Moreover, everything depends on what kind of a man he is (— the greater his stature, the higher the level of repentance required of him), and on the time and place in which he now stands, as is known to the knowing.
Whenever and wherever one is less tempted by a particular sin, a deeper and loftier level of repentance is expected of him for having committed that sin, than at a time when he is more strongly tempted, and must fight more insistently to resist that temptation. Similarly time and place create other differences with respect to repentance. Therefore, judging by one’s present situation, his earlier repentance may be inadequate in erasing his past sins. Perhaps, then, the absence of a higher form of repentance required of him now causes his sins to interpose between himself and G‑d, preventing the light of his soul from penetrating his heart — as the Alter Rebbe continues:
ולכן עכשיו בשעה זו, שרואה בעצמו דלא סליק ביה נהורא דנשמתא, מכלל שהיום לא נתקבלה תשובתו, ועונותיו מבדילים, או שרוצים להעלותו לתשובה עילאה יותר, מעומקא דלבא יותר
Consequently, now, at this time, when observing himself he sees that “the light of the soul does not penetrate into him,” it is evident that either, (a) his repentance has not been accepted, and his sins still separate him from G‑dliness; or (b) it is desired that he be raised to a more sublime level of repentance, coming from a point yet deeper in his heartthan his earlier repentance.
Far from indicating Divine displeasure, the rejection of his repentance in this latter case points to Divine favor: a desire to raise this person to yet greater heights of repentance. Hence the difficulties in his divine service and the timtum halev — so that he will call forth greater resources from within himself, and repent more deeply.
ולכן אמר דוד: וחטאתי נגדי תמיד
For this reason, King David said, despite the fact that he was a tzaddik, who was also able to say of himself: 1 “My heart is a void within me,” which means (as Rashicomments, 2 “The evil impulse is as if dead within me,” — despite this he would still say:) 3 “My sin is constantly before me.”
Why was it necessary for a man of David’s caliber to constantly bear in mind his past sins? Surely he had repented for them adequately! Obviously, then, the memory is necessary in order to spur one on to greater heights within the ranks of holiness, to deeper levels of repentance, as said earlier. 4