In the generation of the Exodus from Egypt, Moses ascended Mount Sinai three times. The first was to receive the Torah. The second was to plead with G-d for his forgiveness, after the Jewish people sinned in worshipping the golden calf.

Then, on the first day of Elul - the month immediately preceding Tishrei - Moses ascended the mountain a third time, to invoke G-d's abundant mercy for our complete atonement. He remained there for forty days, until Yom Kippur, when G-d cleansed us completely, as though we had never sinned.

Since then, these days are marked as a special period of Divine Grace, during which our sincere prayers are sure to find favor in the eyes of G-d.