And the LORD said unto Moses, Number all the firstborn of the males of the children of Israel from a month old and upward, and take the number of their names.

Jamieson-Fausset-Brown Bible Commentary

40-51. Number all the first-born of the males of the children of Israel, &c.-The principle on which the enumeration of the Levites had been made was now to be applied to the other tribes. The number of their male children, from a month old and upward, was to be reckoned, in order that a comparison might be instituted with that of the Levites, for the formal adoption of the latter as substitutes for the first-born. The Levites, amounting to twenty-two thousand, were given in exchange for an equal number of the first-born from the other tribes, leaving an excess of two hundred seventy-three; and as there were no substitutes for these, they were redeemed at the rate of five shekels for each (Nu 18:15, 16). Every Israelite would naturally wish that his son might be redeemed by a Levite without the payment of this tax, and yet some would have to incur the expense, for there were not Levites enough to make an equal exchange. Jewish writers say the matter was determined by lot, in this manner: Moses put into an urn twenty-two thousand pieces of parchment, on each of which he wrote "a son of Levi," and two hundred seventy-three more, containing the words, "five shekels." These being shaken, he ordered each of the first-born to put in his hand and take out a slip. If it contained the first inscription, the boy was redeemed by a Levite; if the latter, the parent had to pay. The ransom-money, which, reckoning the shekel at half a crown, would amount to 12s. 6d. each, was appropriated to the use of the sanctuary. The excess of the general over the Levitical first-born is so small, that the only way of accounting for it is, by supposing those first-born only were counted as were males remaining in their parents' household, or that those first-born only were numbered which had been born since the departure from Egypt, when God claimed all the first-born as his special property.

Matthew Henry's Concise Commentary

3:40-51 The number of the first-born, and that of the Levites, came near to each other. Known unto God are all his works beforehand; there is an exact proportion between them, and so it will appear, when they are compared together. The small number of first-born, over and above the number of the Levites, were to be redeemed, and the redemption-money given to Aaron. The church is called the church of the first-born, which is redeemed, not as they were, with silver and gold; but, being devoted by sin to the justice of God, is ransomed with the precious blood of the Son of God. All men are the Lord's by creation, and all true christians are his by redemption. Each should know his own post and duty; nor can any service required by such a Master be rightly accounted mean or hard.

Matthew Henry's Whole Bible Commentary

Verses 40-51

Here is the exchange made of the Levites for the first-born. 1. The first-born were numbered from a month old, v. 42, 43. Those certainly were not reckoned who, though first-born, had become heads of families themselves, but those only that were under age; and the learned bishop Patrick is decidedly of opinion that none were numbered but those only that were born since their coming out of Egypt, when the first-born were sanctified, Ex. 13:2. If there were 22,000 first-born males, we may suppose as many females, and all these brought forth in the first year after they came out of Egypt, we must hence infer that in the last year of their servitude, even when it was in the greatest extremity, there were abundance of marriages made among the Israelites; they were not discouraged by the present distress, but married in faith, expecting that God would shortly visit them with mercy, and that their children, though born in bondage, should live in liberty and honour. And it was a token of good to them, an evidence that they were blessed of the Lord, that they were not only kept alive, but greatly increased, in a barren wilderness. 2. The number of the first-born, and that of the Levites, by a special providence, came pretty near to each other; thus, when he divided the nations, he set the bounds of the people according to the number of the children of Israel, Deu. 32:8. Known unto God are all his works beforehand, and there is an exact proportion between them, and so it will appear when they come to be compared. The Levites' cattle are said to be taken instead of the firstlings of the cattle of the children of Israel, that is, the Levites, with all their possessions, were devoted to God instead of the first-born and all theirs; for, when we give ourselves to God, all we have passes as appurtenances with the premises. 3. The small number of first-born which exceeded the number of the Levites (273 in all) were to be redeemed, at five shekels apiece, and the redemption-money given to Aaron; for it would not do well to have them added to the Levites. It is probable that in the exchange they began with the eldest of the first-born, and so downward, so that those were to be redeemed with money who were the 273 youngest of the first-born; more likely so than either that it was determined by lot or that the money was paid out of the public stock. The church is called the church of the first-born, which is redeemed, not as these were, with silver and gold, but, being devoted by sin to the justice of God, is ransomed with the precious blood of the Son of God.