Our Parshah tells a story of twelve agents sent by Moshe to Israel. The Torah testifies that they first embarked with noble intentions despite their later submission of a negative report, which drove the nation to despair. In Rashi’s words, “they were kosher at that hour.” Why does Rashi specify that they were kosher for an hour?
Forty Days = Forty Years
In punishment for the nation believing the negative report, G‑d decreed that they would wander the desert for forty years before entering the land.
We know that the agents journeyed the length and breath of Israel for a period of forty days. By this count, the people were punished on a scale of one year per day of the agents’ journey. Accordingly, every hour of their journey cost the nation half a month of wandering.
However a problem arises when you consider the actual length of our ancestors’ stay in the desert. They embarked on the fourteenth of Nissan and arrived in Israel forty years later, on the tenth of Nissan. By this count, four days were missing from the forty-year total!
Furthermore, by the Torah’s own testimony, it is an eleven-day journey from Sinai to Israel. In all fairness, those eleven days should also be deducted, because they would have traveled during those days even if they were not punished.
It appears that a total of fifteen days were deducted from the forty-year decree. Unless you consider that the agents were righteous, and had kosher intentions, during the first hour. In that case the nation would naturally not be punished for that hour of the agents’ journey, rightfully deducting half a month from the overall total.
With a single word, Rashi helps us understand why the forty-year decree was in fact minus fifteen days.

Point well taken so here is the reason for the article.
If you believe the Torah is man written there is no reason to be didactic about such detail. But if you believe it is G-d written, you must believe that it is as perfect as G-d is. G-d would not produce an imperfect document.
When you see a discrepancy alike this, a punishment short by fifteen days, you have to wonder why G-d wrote an untruth in His Torah. If it were written by man, it could be excused as a manner of speaking, but not for G-d. The essence of truth, would not tolerate an untruth.
This calculation and others like it go to the heart of our faith in the Torah as a G-d written.
When we see Rashi provide a detail that is a, without source and b, seemingly unnecessary, it behooves us to delve into why he wrote it. Rashi was of course fallible, but we know he was careful with his words.
Finding an answer to both questions in one fell swoop is nothing short of brilliant. That is why this author chose to share the insight.