This is another important point to draw your attention to from this verse. According to Afosa.org, there are certain matters in this world, which we really do not know. Not everything in this world and all its secrets and reality is completely exposed to us.
a. The number 40 appears to have special secrets associated with it, because the question of 40 is not only in the case of Nabi Moosa (a.s), but also at the same time in the case of Nabi Nuh (a.s), the flood was for forty days.
b. Furthermore, we also read in history that the people of Nabi Moosa (a.s), namely the Israelites, were lost for 40 years.
c. We also know that before our beloved Prophet Muhammad (SAWA) received revelation, he secluded himself for 40 days (I’tikaaf) from his wife, Lady Khadijah (s.a).
d. Also, Rasulullah (SAWA) was appointed to be a Prophet at the age of 40.
e. There are also Hadith narrations, which state that if you want to achieve perfection and success in your life, then it should be by the age of 40, as it becomes difficult thereafter.
f. Then there are also Hadith, which state that if someone makes their intentions sincere for 40 days, then Almighty Allah (SWT) grants such a person wisdom.
g. Similarly, the punishment for certain sins in this world is 40 days.
h. Then also when performing Tahajjud, one is recommended to make dua for 40 believers.
i. When someone dies, it is recommended to place in his/her kafan (burial shroud), a letter of attestation from 40 witnesses testifying that the deceased was a true believer (mu’min).
This list of narrations from Quran and Hadith regarding the emphasis on the number 40 can go on and on. Suffice to say that this is another interesting aspect of the above quoted verses of the Holy Quran.