Charles Ellicott Commentary Numbers 3:43

"And all the first-born males according to the number of names, from a month old and upward, of those that were numbered of them, were twenty and two thousand two hundred and threescore and thirteen." — Numbers 3:43 (ASV)

Twenty-two thousand two hundred and seventy-three. —The extremely small number of firstborn in proportion to a male population of 600,000 aged twenty years and upward—i.e., to a total male population of about 1,000,000—has been a significant source of difficulty. In some cases, this has served as a reason for rejecting the historical truth of the narrative, which, it has been alleged, involves the incredible conclusion that there was only one firstborn to forty-four males.

In response to those who present this difficulty as a reason for rejecting the narrative's truth, it might be sufficient to reply that it is difficult, if not impossible, to imagine that a writer who recorded (or, according to this theory, invented) so many complicated calculations would have inserted among them one so fraught with apparent improbability. Many solutions to the problem have been proposed that address the apparent disproportion in the number of firstborn, relieving it not only of its alleged impossibility but also of its improbability. Some have argued that we are compelled by every principle of analogy to restrict the firstborn sons to those under twenty years of age, who had not been included in the census already taken.

The destruction of the Egyptian firstborn was clearly subject to a somewhat similar limitation. Pharaoh himself was, in all probability, a firstborn son. Regarding the Egyptians generally, there does not appear to have been more than one death in each house (Exodus 12:30), although there must have been many houses in which the father (and perhaps the grandfather), as well as the son, was a firstborn child. Another opinion is that by "the firstborn in every family" we are to understand the firstborn in every household, including the children of concubines and slaves.

On either of these hypotheses, when due allowance is made for the average proportion of the sexes, the average number of early deaths, and the limitation of the term firstborn to those who were firstborn from both the father and the mother, it has been argued that the number of firstborn is consistent with the supposition that each Israelite family had about eight or nine children. This supposition, considering how prolific the Hebrew women are said to have been, cannot be dismissed as incredible. However, the most probable solution to the difficulty appears to be the one given in the Introduction.