“Do not cook a young goat in its mother’s milk." (Exodus 23:19 NIV)
For the life of me I can't discern any practical or spiritual significance in this one.
If I understand correctly this is where Jews get their (misguided?) prohibition against having cheese on a hamburger (mixing milk and meat products).
From what I have gathered, this prohibition is said 3 times in the Torah (Exodus 23:19; Exodus 34:26; Deuteronomy 14:21). The two passages in Exodus mirror each other, and the surrounding context implies it has to do with the pilgrimage Feasts sacrifices. The passage in Deuteronomy the previous context appears different, but the passages following Deuteronomy 14:21 speak to the offering of first fruits and the Feast of Succot. It is clear, that the boil a goat in it's mother's milk was a matter of sacrifice, not dietary laws. So how did this tradition of separating cheese and meat come from?
Some possibilities suggest after the destruction on the Temple and failure of the Jewish revolt under Bar Kochbah, the rabbis began the process of transferring Temple service to daily life within the synagogue communities of the Diaspora. In the same way they transferred what was a temple law, to being a dietary law. It is unclear whether the prohibition made by the rabbis to separate milk and cheese was pre-temple or post temple destruction, but it is clear it was taken out of the biblical context of sacrifice, and into a dietary law based on the preceeding passages in Deuteronomy 14:21 being of
kashrut laws. It appears the rabbis solely looked at this passage through the lens of the Deuteronomy passage, neglecting the passages in Exodus consisting of temple worship.
Another possibility could be within rabbinic Judaism, the need to mark distinctions between the synagogue and the emerging Christian church became increasingly important. Making the complete separation of meat and milk an essential element of
kashrut laws would have made social interaction with non-Jews via table fellowship a near impossibility.
Rabbinic literature offers little to no commentary on Genesis 18:1-8 on when Jesus, I mean The Lord, appeared to Abraham, and Abraham served his guests meat and milk. This is probably because prior to the destruction of the temple, the concern was cooking meat in milk, not in eating the two together.
Although the Mishnah attributes the concerns of the House of Hillel and Shammai, rabbis living in the pre-destruction era of the temple. That the Mishnah would portray Hillel and Shammai as concerned with meat and milk being a dietary prohibition, which in the biblical context of the Torah is about sacrificial service, agrees with a common phenomenon of the later rabbis attributing their newly formed
halachah to earlier authorities in order to give it greater weight. Which we all do at times when we say, "Well my dad said this..." It's the same idea.
So that's just a brief summary of how I found this commandment evolved from a sacrificial commandment from God, to a man-made dietary commandment.