(12) Thou shalt set apart--i.e., separate off from the rest of the flock or herd, that it might not be mixed up with those which were not "sanctified."

Verse 12. - Set apart. The expression is especially appropriate to the case of first-born animals, which would have to be separated off from the rest of the flock, or of the herd, and "put aside" for Jehovah, so as not to be mixed up and confounded with the other lambs, kids, and calves. The males shall be the Lord's. This limitation, implied in verse 2, is here brought prominently into notice.

13:11-16 The firstlings of beast not used in sacrifice, were to be changed for others so used, or they were to be destroyed. Our souls are forfeited to God's justice, and unless ransomed by the sacrifice of Christ, will certainly perish. These institutions would continually remind them of their duty, to love and serve the Lord. In like manner, baptism and the Lord's supper, if explained and attended to, would remind us, and give us occasion to remind one another of our profession and duty.That thou shalt set apart unto the Lord all that openeth the matrix,.... Or "the womb", as in Exodus 13:2, and this phrase, "set apart", explains the word "sanctify" there, and shows that it signifies the separating of such to the use and service of God, causing it to "pass", as the word (d) here used signifies, from a man's own power and use, to be the Lord's only:

and every firstling that cometh from a beast which thou hast; or "even every firstling" (e), explaining what is meant by what opens the matrix or womb, even every firstborn of a beast; though Jarchi interprets it of an abortion, what comes before its time, that this also should be set apart to the Lord; this must be understood of the firstlings of clean creatures, fit for food and sacrifice, such as the firstlings of cows, sheep, and goats, Numbers 18:17 as distinguished from unclean ones in the following verse:

the males shall be the Lord's; which explains what sort of firstborn of man and beast were to be set apart for his use, not females, though the first that opened the womb; but males.

(d) "et transire facies", Pagninus, Montanus, Fagius, Vatablus, Drusius, Cartwright; so Ainsworth. (e) "etiam quicunque vel quicquid aperuerit", Junius & Tremellius, Piscator, Ainsworth.