ב"ה, י"ט מנחם אב, ה'תשי"ד
ברוקלין, נ.י.
שלום וברכה!
... מה ששואל אודות לימוד היום-יומי של שיעור חומש עם פירש"י הנה מובן הכוונה שבזה הוא דבר יום ביומו, ומובן ג"כ שבאונס הרי יש להשלים בלילה שאחרי היום או גם במשך השבוע...
בברכה.
B"H, 19 Menachem Av, 5714.
Brooklyn, NY.
Shalom u'Vrachah!
... Regarding your question about the daily study of the Chumash portion with Rashi's commentary: it is understood that the intention is for this to be done each day in its time. However, it is also clear that if one is prevented from doing so due to circumstances beyond their control, they may make it up at night following that day or even during the week...
With blessing.
Summary
The Rebbe teaches that while daily Chumash study should ideally be done on its assigned day, if missed due to unavoidable circumstances, one may make up the portion at night or later in the week.