"51 Days of Salvation" - The Secret of the Days of Mercy Revealed!
As the Aderet Eliyahu (Rabbi Yosef Chaim, the Ben Ish Chai) writes: He says that these 51 awesome days—from Rosh Chodesh Elul through Simchat Torah—are a sign and an aid for the entire year. If a person guards them, he will overcome his evil inclination (Yetzer HaRa) and overcome his trials. But if not—woe to him, he will be trapped in the net of the evil inclination.
As the Aderet Eliyahu (Rabbi Yosef Chaim, the Ben Ish Chai) writes: He says that these 51 awesome days—from Rosh Chodesh Elul through Simchat Torah—are a sign and an aid for the entire year. If a person guards them, he will overcome his evil inclination (Yetzer HaRa) and overcome his trials. But if not—woe to him, he will be trapped in the net of the evil inclination.
So he writes there: What did Avraham our Father say to Lot? "Please separate from me: if you go to the left, I will go to the right; and if you go to the right, I will go to the left" (Genesis 13:9). The Hebrew word NA (נָא - "Please") equals 51 in gematria!
We ask the evil inclination: Listen my friend, "Separate NA"—Lot represents the evil inclination—leave us alone for these 51 days! "If to the left, then I will go to the right"—if you go toward the good, right side, "then I will go left," meaning we will subdue the left side. But "if to the right"—if you try to lead using the left side, the evil inclination—"then I will go left," and even the right side, the good inclination (Yetzer HaTov), Heaven forbid, will end up going there. Therefore, one must be very careful during these 51 days.
"Let me cross over, PLEASE (NA), and see the good land" (Deuteronomy 3:25). The Holy One, Blessed be He, said to Moshe: If you ask "Let me cross over" (Ev'rah), then nullify "Forgive, please" (Selach NA). If you want "Forgive, please" (Selach NA), then nullify "Let me cross over" (Ev'rah).
So the Ben Ish Chai explains: NA (51) refers to these days. If a person lacks strength and says, "Look, I want to pass over these NA [51] days, let these days just pass already"—then "Forgive, please" (Selach NA) is nullified! There will be no forgiveness! How will he be atoned for if he just wants them to pass by? But if you want "Forgive, please" (Selach NA)—if you want pardon and forgiveness during these 51 days—then nullify "Let me cross over, please" (Ev'rah NA). Do not wish to just pass over these 51 days, and do not listen to the voice of the evil inclination!