ציטירנדיקער פּירוש אויף במדבר 1:19

לכפר על נפשותיכם, “to atone for your souls.” Some commentators claim that as long as the silver from this contribution remained in existence, there was no need to make another such contribution when a census would be taken. This is why no mention is made of a further contribution when the Israelites were counted once more in the 40th year after the debacle at Shittim, and Pinchas’ slaying the prince of Shimon, Zimri. (Numbers 25,13) By the time another census was taken some 400 years later in the time of David, this silver even if it still existed, could no longer be identified and therefore the soldiers who had been counted in that census were punished by a plague.

ואת כל העדה הקהילו באחד לחדש השני, “They gathered together the entire assembly on the first of the second month;” On the very day G’d spoke to Moses, Moses and Aaron assembled the entire people and began to organise and count them; however, the count was not completed in a single day. This is why the Torah had to write: “he numbered them in the desert of Sinai“ (verse 19). He completed the count in the same spot though not on the same date. This is the view of Nachmanides.

AND THEY ASSEMBLED ALL THE CONGREGATION TOGETHER ON THE FIRST DAY OF THE SECOND MONTH. Scripture mentions [the date although it is already stated in Verse 1 above, to indicate] the zeal of our teacher Moses in [fulfilling] the command of G-d for on the very day of the communication [that he was to take a census of the people] he took the princes of the tribes and assembled all the congregation and began to count them. The count, however, was not completed in one day, and therefore He states again, so did he number them in the wilderness of Sinai,⁵⁷Verse 19. in order to inform [us] that the counting was all done in that place, but was not all [finished] on that day.