Numbers 1:18 (BSB)

and on the first day of the second month they assembled the whole congregation and recorded their ancestry by clans and families, counting one by one the names of those twenty years of age or older,

From Numbers 1. Also in the ESV.

Commentary on Numbers 1:18

• Matthew Henry (Presbyterian), Matthew Henry's Complete Commentary on Numbers 1:17-43: We have here the speedy execution of the orders given for the numbering of the people. It was begun the same day that the orders were given, The first day of the second month; compare Num 1:18 with Num 1:1. Note, When any work is to be done for God it is good to set about it quickly, while the sense of duty is strong and pressing.
• John Gill (Reformed Baptist), Exposition of the Old and New Testaments on Numbers 1:18: And they assembled all the congregation together on the first day of the second month,.... The month Ijar, as the Targum of Jonathan, answering to part of April and May: this was done on the selfsame day the Lord spake unto Moses about this affair, Num 1:1; so expeditious were he and Aaron in doing the will of God: and they declared their pedigrees; either...
• Jamieson-Fausset-Brown (Reformed), Commentary Critical and Explanatory on the Whole Bible on Numbers 1:18: by their polls--individually, one by one.
• Geneva Bible Notes (Reformed), Geneva Bible Study Notes on Numbers 1:18: And they assembled all the congregation together on the first [day] of the second month, and they declared their pedigrees after their families, by the house of their fathers, according to the number of the names, from twenty years old and upward, by their polls. (f) In showing every man his tribe and his ancestors.