The answer to this question may seem simple—because Jesus spent 40 days in the desert, resisting the temptations of Satan in order to begin His public ministry following His Baptism. But how do we know it was 40 days? It’s a reasonable question, and if this were the only instance of the number 40 appearing significantly in the Bible, we might just say “because that’s how long the process took.”
However, it is because the number 40 appears so frequently in the Bible that the number appears at once both random and yet completely deliberate.
For example, here are just a few instances of the number 40 appearing in the Bible:
l The world is flooded by rain for 40 days (Genesis 7:4).
lThe Israelites wandered the wilderness for 40 years (Exodus 16:35).
lAfter leading the Israelites out of Egypt, Moses spent 40 days with God on the mountain without food or water (Exodus 24:18, 34:28).
lJesus remained on Earth for 40 days before his Ascension (Acts 1:3).
Knowing God intended for these instances to transpire exactly as they did, why 40? The Bible makes no explicit mention of the number’s significance, and of course there are several other numbers which are notably common in the Bible, such as three and seven.
Many people who have taken note of these patterns have delved into “Biblical numerology,” which is an attempt to “decode” the Bible and find additional spiritual truths hidden within—a risky business, as it veers towards the heresy of Gnosticism, in which salvation is achieved through “secret knowledge,” rather than through faith in Christ.
Instead, we should interpret these numbers similarly to how Jesus speaks in parables—symbols and narratives often carry more weight in our minds than simple statements. Therefore, the most likely explanation for the recurrence of certain numbers is for the purpose of drawing our attention to the significance of certain events within the concept of covenant theology.
Thus, we can surmise that the use of the number 40 corresponds with the fulfillment of promises made by God and highlights periods of trial and tribulation. Furthermore, it should encourage us to delve deeper and consider the fact that these trials are indeed a necessary part of our own salvation, and that God’s consolation is waiting for us on the other side of that trial. For example, an easy comparison can be made between the 40-year wandering of the Israelites and Jesus’ 40 days in the desert. Within those periods, there was a process of purification; God allowed the sinful generation of Israelites to perish before their descendants came into Israel, and Jesus overcame the temptations which overwhelmed Adam and Eve, establishing Him, as Saint Augustine puts it, as a “mediator in overcoming temptations, not only by helping us, but also by giving us an example.”
So while it’s certainly possible that these events each occurred within a specific 40-unit span, perhaps the use of 40 is more about symbolic resonance and artistic perfection than simply an arbitrary description of time.
And here’s a bonus fact for you—Lent is technically 46 days, since Sundays are feast days and are not included as “fasting” days. Thus, sometime before the ninth century, it became commonplace to begin the fast on Ash Wednesday, to account for the feast days every Sunday, bringing the total number of fast days to 40.
