Musar su Esodo 12:37

Moses understood that this commandment was for all time, an error on his part. He asked himself that if the commandment were a one-time commandment in order to let him know how many Jews had died as a result of the golden calf, he would not be able to see how such a count would provide proof positive for there had not been a previous census to compare the new figures with. While it is true that the Torah (Exodus 12,37) had given a round figure of 600,000 men of military age at the time of the Exodus, Moses did not know about this because the Torah had not yet been written down. Moses' question then was: "How can this commandment be performed in the future when the promise that the Jewish people will be so numerous that they cannot be counted will have become true?" Moses did not have a problem with the commandment as it applied at that time. G–d informed him that his difficulty was due to the faulty premise that there would be an annual census. The Israelites had to be counted now so that the number who had died during the tragic golden calf episode could be established.