Sforno on Numbers 1:47/ספורנו על במדבר א׳:מ״ז

1לא התפקדו, were not counted by the officials appointed to conduct the census, nor did they count themselves. (compare Ibn Ezra on this) They had not prepared themselves as had the other people for coming to the assembly point and providing documents proving their identity and genealogy. What is mentioned in this verse all referred to the time prior to G’d announcing in verse 49 that the tribe of Levi should not be included in this census. The Levites had been awaiting instructions concerning how they were going to be counted. The reason they had reason to wonder was that the tribe of Levi had not been mentioned in the list of tribes during this entire chapter when the Torah referred to “each man per each tribe” in verse 4.