The choice of 40 days for transformative practice is significant. Kundalini yoga teaches us that it takes 40 days to change behaviour to create new patterns or habits. Forty days holds both a mystical and practical significance. The number 40 has sacred relevance in several religions.

Sacred and Mystical Significance of 40 Days

In the Sufi religion seekers may participate in Chilla or Khalwa, a 40-day spiritual retreat of penance and solitude. In Judaism, it is taught that if one seeks an answer to their prayers, they should say the same prayer for 40 days. The Old Testament tells us that rain fell for 40 days and 40 nights while Noah’s Ark protected his family and the animals (Old Testament Genesis 7:4). When the rain stopped, Noah waited 40 days before releasing a raven from the Ark. (Genesis 8:5-7).

We are also told in the Old Testament and the Islamic Quran that that Moses, who was summoned by God at age 40, spent 40 days on Mount Sinai when he received the Ten Commandments and lived 40 years in Egypt and 40 years in the desert. Similarly, the Islamic religion teaches that Muhammad was 40 years old when he received the revelation from the angel Gabriel that he was to be a prophet destined to teach the new Islamic religion for the balance of his life.

Other examples of the significance of the number 40 in the Old Testament include the 40-year reigns of Saul, David and Solomon and the great prophet Elijah’s journey to the Mount which took 40 days and 40 nights. Also, the Jewish people were forced to wander the desert for 40 years as a punishment for doubt and disobedience. (Numbers 14:34) In the New Testament, we learn that Jesus fasted for 40 days and 40 nights in the desert while tempted by Satan. Successful in his resistance, he began his ministry thereafter. (New Testament, Matthew 4:2, Mark 1:13 and Luke 4:2) Forty days is also the time between the Resurrection and the Ascension (New Testament, Luke 24) Lent is a Christian religious practice of abstinence and penitence in commemoration of the time between the crucifixion and ascension, Jesus’ time of fasting in the desert, and a celebration of the gift of Jesus’ teachings. The period of mourning in the Greek-orthodox religion is 40 days during which the close family continue to wear black and there is no socializing. In strict practice, the men close to the deceased do not shave for 40 days.

Mathematics and Science: 40 as a Significant Number

There are also examples in mathematics, science, and biology where 40 is a significant number. Forty happens to be the number of weeks of human gestation. In physiology, our skin cells on average take 40 days to renew and our red blood cells start dying from 40 days onwards. The only time the same number occurs in the Celsius and Fahrenheit temperature systems is negative 40. Forty is a cardinal, positive, whole number. It is a square number and a composite number with multiple factors. It is the ninth semi-perfect number and the ninth refactorable number.

40 in Everyday Life and Culture

Other interesting notes about the number 40 include the following: In literature we read about Ali Baba and his 40 Thieves. We have been told that a perfect nap is “40 winks”. The standard American work week is 40 hours. Forty is the only number in the English language where the letters of the word appear in alphabetical order. The Italian word for 40 is “quaranta”. During the bubonic plague, 40 days was the term of quarantine. The most recent Covid pandemic took hold in 2020. (20+20=40)