In simple words fast in the way that we understand it on this earth. In contrast to that which it says (Tehilim 90:4) כִי אֶלֶף שָנִים בְעֵינֶיךָ כְיוֹם א֖תְמוֹל כִי יַעֲבֹר וְאַשְמוּרָה בַלָיְלָה “For a thousand years are in Your eyes like yesterday, which passed, and a watch in the night” and Rashi writes: A thousand years of man are like one day of the Holy One, blessed be He, and part of the night with it; for one day of Hakodosh Boruch Hu, and a little of the night of Hakodosh Boruch Hu, are a thousand years, for the text does not say that the day of Hakodosh Boruch Hu, is like a thousand years, but that when a little of the night elapses with it, then His day is complete, and it is a thousand years.
