Matthew Poole's Concise Commentary
Exodus 23:19
This seems to be a general rule, extending to all the fruits which the earth first produced; in every kind of which the very first are here enjoined to be offered unto God, before they should presume to eat any of them. It may seem to be repeated here, where the year of rest is mentioned to leach them the first-fruits were to be given to God of all that the earth produced, not only by their labour and seed, as might be thought from Exodus 23:16, but also of its own accord, as is here implied. He names one kind, under which he understands a lamb, or a calf, &c., according to the use of Scripture style. This law many understand literally, and that it is forbidden to them, because the idolaters had such a custom, whereof yet there seems to be no sufficient proof; nor, if there were, doth it seem to be a rite of that importance or probability to entice the Israelites to imitate it, that there needed a particular law against this, more than against a hundred such ridiculous usages which were among the heathen, and are not taken notice of in the book of God's laws. The words may be rendered thus, Thou shalt not seethe, or roast, (for the word bashal signifies to roast as well as to boil, as it is evident from Deuteronomy 16:7) a kid, being, or whilst it is (which is to be understood, there being nothing more common than an ellipsis of the verb substantive) in his mother's milk; which it may be said to be, either,
1. Whilst it sucks its mother's milk; and so it may admit of a twofold interpretation: (1.) That this is to be understood of the passover, of which most conceive he had now spoken, Exodus 23:18, in which they used either a lamb or a kid, Exodus 12:5, and then the word bashal must be rendered roast. (2.) That this speaks not of sacrifice to God, wherein sucking creatures were allowed, Exodus 22:30 Leviticus 22:27 1 Samuel 7:9, but of man's use; and so God ordained this, partly because this was unwholesome food, and principally to restrain cruelty, even towards brute creatures, and luxury in the use of them. Or rather,
2. Whilst it is very tender and young, rather of a milky than of a fleshy substance, like that young kid of which Juvenal thus speaks, Qui plus lactis habet quam sanguinis, i.e. which hath more milk than blood in it. And it may he said to be in its mother's milk, by a usual hypallage, when its mother's milk is in it, i.e. whilst the milk it sucks as it were, remains in it undigested and unconverted into flesh, even as a man is oft said to be in the Spirit, when indeed the Spirit is in him. And what is here indefinitely prohibited, is elsewhere particularly explained, and the time defined, to wit, that it be not offered to God before it was eight days old. And this interpretation may receive light and strength from hence, that the law of the firstfruits, which both here and Exodus 34:26 goes immediately before this law, doth in Exodus 22:30 immediately go before that law of not offering them before the eighth day, which implies, that both of them speak concerning the same thing, to wit, the first-fruits or first-born of the cattle, which were not to be offered to God while they were in their mother's milk, saith this place, or till they were eight days old, saith that place. And consequently, if they might not be offered to God, they might not be used by men for food.