And Moses and Aaron took these men,.... They doubtless sent for them, and acquainted them with the nomination of them, by the Lord himself, for such a service; and they took them with them to the place where the number of the people was to be taken:
which are expressed by their names: in Numbers 1:16, and that as declared by the mouth of God himself.

This command was carried out by Moses and Aaron. They took for this purpose the twelve heads of tribes who are pointed out (see at Leviticus 24:11) by name, and had the whole congregation gathered together by them and enrolled in genealogical tables. התילּד, to announce themselves as born, i.e., to have themselves entered in genealogical registers (books of generations). This entry is called a פּקד, mustering, in Numbers 1:19, etc. In vv. 20-43 the number is given of those who were mustered of all the different tribes, and in Numbers 1:44-47 the total of the whole nation, with the exception of the tribe of Levi. "Their generations" (Numbers 1:20, Numbers 1:22, Numbers 1:24, etc.), i.e., those who were begotten by them, so that "the sons of Reuben, Simeon," etc., are mentioned as the fathers from whom the mishpachoth and fathers' houses had sprung. The ל before שׁמעון בּני in Numbers 1:22, and the following names (in Numbers 1:24, Numbers 1:26, etc.), signifies "with regard to" (as in Isaiah 32:1; Psalm 17:4, etc.).