Counting a massive population is always a logistical challenge, but counting the Levites presented a deeply unique hurdle. While the adults of other Israelite tribes could simply present themselves to their leaders to be registered, this specific census required the inclusion of babies and young children. In this context, a child was considered an infant from the moment of birth until the age of thirteen [ברכת אשר על התורה]. Because these children could not present themselves, the situation demanded direct divine intervention, and the counting was ultimately carried out with the help of God [ביאור שטיינזלץ].
Tasked with this enormous responsibility, Moses turned to God, questioning how he could possibly enter private family tents to determine the number of nursing infants. God instructed him to do his part, promising that He would complete the rest of the work. Moses stood at the entrance of each tent, and the Divine Presence went before him. For the older children, Moses likely asked that they be brought outside so he could count them directly [ברכת אשר על התורה].
As for how Moses learned the exact number of infants remaining inside, the primary approach among commentators is that a heavenly voice emerged from within the tent, announcing the precise count to him [רש"י, מלבי"ם]. Another perspective suggests that Moses was overcome with an abundance of the Holy Spirit, much like the moment of receiving a prophetic command. Through this divine inspiration, he inherently knew exactly who was inside each tent without ever needing to step foot inside [העמק דבר].
The reason behind Moses' hesitation to enter the tents in the first place is a matter of discussion. One view sees his reluctance as a supreme expression of modesty, noting that it is inappropriate and unseemly for a Torah scholar to enter another person's private quarters where women are present [גור אריה, שפתי חכמים]. Conversely, another viewpoint argues that his hesitation did not stem from modesty, but rather from the sheer physical burden of the task. Entering every single tent and reaching every crib would have been an overwhelming physical strain, especially since Moses was required to conduct this census entirely alone, without the assistance of the family leaders [ברכת אשר על התורה].