How to Change Your Mazal in 40 Days or 960 Hours
How can one change one's mazal, and why is it customary in Judaism to pray for 40 days in certain circumstances? Chazal teach that when a person prays for something important and cannot receive an answer for a long time, he should pray for 40 days. And 40 days multiplied by 24 hours = 960 hours. What is 960? Neither more nor less than the gematria of the word "Shamayim". In other words, after reciting a certain prayer for 960 hours, one can knock on the gates of Heaven—Shamayim.
Why specifically 40 days?
1. The embryo takes the form of a "vlad" (fetus) on the fortieth day. The word "vlad" has a gematria of 40;
2. Moshe Rabbeinu ascended to Heaven and, for 40 days, neither ate bread nor drank water, in order to attain the state of an angel and receive the Torah;
3. A mikveh taharah has the power to purify only when it contains 40 se'ah of water (equivalent to 24 log);
4. Chazal teach that the primary force distinguishing a "kadosh" (holy person) from an "arel" (uncircumcised, unholy person) comes from the Oral Torah even more than from the Written Torah. This is expressed in the word "Mishnah" (in the Gemara it appears under the name "matnitin", whose gematria is 960, and it transforms the "arel" into a "kadosh").
5. According to the Jerusalem Talmud, a whole insect (briyah) does not become "batel be-shishim" (that is, rendered permissible when it falls into food), but it does become so when diluted to 1/960 (which is not the ruling according to the Babylonian Talmud).
6. Rabbi Elimelech of Lizhensk writes in his book "Noam Elimelech" that a person needs 40 days for a new behavior to become a habit and turn into a "middah"—a character trait;
7. 40 days separate Rosh Chodesh Elul from Yom Kippur—the days of Selichot;
8. The Flood lasted 40 days;
9. The People of Israel had to travel through the wilderness for 40 years;
10. Forty days before conception, it is known who a person's destined bride will be.
The common denominator of all these examples is the ability of a person to change a "gezeirah" in 40 days, multiplied by 24 hours, which equals exactly 960 hours. In other words, a person can change his "mazal", the course of his destiny, and turn the situation around by undertaking a 40-day commitment.
(silatehilim.com translation of material from the blog post "Shirat Dvora")
