Charles Ellicott Commentary Exodus 12:21

"Then Moses called for all the elders of Israel, and said unto them, Draw out, and take you lambs according to your families, and kill the passover." — Exodus 12:21 (ASV)

THE FIRST PASSOVER KEPT.

Moses called for all the elders. —He had been directed to speak unto all the congregation (Exodus 12:3), but understood the direction as allowing him to do so mediately, through the elders.

Draw out. —Some understand this intransitively—“Withdraw, and take,” i.e., go, and take; others transitively—“Withdraw a lamb from the flock.”

According to your families —i.e., with reference to the number of your families, but not necessarily one for each. (See Exodus 12:4.)