“Count the children of Levi...from the age of one month and upward...Moshe counted them according to the word of Hashem as he was commanded” (Bemidbar Sinai 3:15-16).
Rashi explains the phrase “according to the word of Hashem” as indicating that Moshe had asked, “How can I determine the number of infants in each family? Am I to enter people's tents and invade their privacy?” To this Hashem responded, “You do your task and I will do Mine. You are to stand in front of the door of each tent, and I will tell you the number of infants therein.”
One might ask, “If determining the number of Leviim was dependent upon Divine revelation, why was there a need for Moshe to do anything at all? Why did Hashem not simply tell Moshe how many Leviim there were?” The answer to this question is essentially the formula for man's actions in this world. An omnipotent God can do everything, and is hardly in need of humans. For reasons known only to the Divine wisdom, man was placed on earth with a mission that only he can achieve, and it is his responsibility to fulfill that mission. If the fulfillment of that mission appears to be beyond the scope of man's capacities, this does not exempt man from doing his utmost toward reaching the goal. Man must do whatever he can, and whatever is truly beyond him becomes the responsibility of Hashem. This principle is stated in Pirkei Avot (2:16): “It is not up to you to complete the work, yet you are not free to desist from it.”
We may now understand the verse preceding this command to Moshe: “Hashem spoke to Moshe in the wilderness of Sinai, saying (לאמר), ‘Take a count of the children of Levi.’” Whenever the Torah says לאמר, it means that Moshe was to relay that message. But to whom was this message to be relayed, inasmuch as it was only Moshe who was instructed to take the count?
The answer is that Moshe was to relay the content of this commandment to Bnai Yisrael and to all further generations: “You do your task, and I will do Mine.” We, today, as Moshe then, must not retreat from any Mitzva, even if its fulfillment appears to be beyond our means. We are obligated to do that which we can and leave the rest to Hashem. (Adapted from Living Each Week)