Flying creatures only have to be herbivores, and land creatures that were herbivores that chewed cud (regurgitated grass) and had split hooves were considered clean. Land and air creatures that were omnivores, carnivores, and scavengers were all classified as unclean. This may have been connected to why humans are forbidden from consuming blood as a moral sin in the Bible (Genesis 9:4, Leviticus 7:25-26, Leviticus 17:10-14, Leviticus 19:26, Deuteronomy 12:16, Deuteronomy 12:22-25, Deuteronomy 15:23, Acts 15:20 & 29). What if animals that eat meat (who consume blood) are classified as sinful in a sense because they don’t drain the blood? Land creatures are even further distinguished by their anatomy (split hooves), which may provide clues into their digestive processes. For example, rabbits are cud chewers, but they also eat their dung, which may be viewed as unclean.
Sea creatures aren’t limited by their diet, but rather by their anatomy. Sea creatures are only required to have both scales and fins to be kosher, and since fish with fins and scales can eat meat, the blood issue must not be a problem here. This could be because the blood spills out and is diffused into the water, and is not consumed as much. Additionally, fish scales limit the absorption of toxins in the water, protecting the fish from becoming toxic. Another thing to notice is that in the Bible, sea creatures were never sacrificed. This is most likely because fish are not commodities, since they live in the water and can’t be farmed or held as investments. There also may be a spiritual aspect to it. A person doesn’t have to ‘kill’ a sea creature. It simply dies when you remove it from the water. I suspect that since the taking of life is not experienced like with an air-breathing animal, it doesn’t have the same effect of showcasing the darkness of sin through slaughter. From what I’ve read online, it seemed pretty rare that cultures sacrificed fish. I found that ancient Taoists and Greeks sometimes sacrificed fish, but not much else.
The clean animals were sacrificed for the sins of humans, so one needs a pure/clean “sinless” animal for sacrifice to take on the sins of the person. So, animals that eat other animals (dead or alive) are possibly seen as being in a “sinful” state because they consume blood. Land herbivores, such as some mammals (rabbits), as well as reptiles and amphibians, are considered unclean since they don’t meet the anatomical requirements. Additionally, creatures that are venomous or poisonous would be off-limits, and many reptiles fall into this category. There are some mammals, such as certain types of shrews, moles, and bats, that are toxic. Some creatures eat things that can make them poisonous at certain times, meaning they can be considered safe to eat but require special preparation as a precaution. Many poisonous birds fit in this category, like Spur-Winged Goose, Hooded and Northern Variable Pitohui, and even Quail. Overall, the anatomy restrictions seem like a way of warning the Israelites about food safety without getting into specifics for each creature.
Quail, specifically, can cause a sickness referred to in the Bible in Numbers 11:31-34 as coturnism. This sickness became so widespread throughout the Mediterranean that the Roman Empire officially banned the eating of quail in the 1st Century CE. It is said that quails are not always poisonous, and this toxicity may come from something Quails eat, possible candidates being hemlock, Hellebore, or woundwort. Quail is kosher since it is not mentioned in Leviticus 11, and it was already designated as food by God in Exodus 16, so cleanliness wasn’t an issue. Typically, poisonous or venomous creatures are in the category of unclean. The Quail poisoning we see in the Bible is limited to Numbers 11, and the Bible says this is because of the Israelites’ sinful attitude towards God, so this is a unique event. The Israelites called the place of the poising Kibroth-hattaavah (graves of the gluttons), so maybe because the people that died were especially gluttonous? It could be that their quail wasn’t appropriately cooked (because those people rushed it), or they simply overate it, which led to toxicity and caused coturnism. Also, it is possible that a flock of toxic quail joined the flock of safe quail, and those wicked people simply got the bad ones. Since everyone didn’t die, God spared the righteous, and therefore, there must have been a distinction among the quail or a distinction between how the people prepared/ate it.
Either way, the kosher food laws are particular and go beyond just health and safety, but also point to the symbolism of sin and death. Sea creatures and Flying creatures were created together on Day 5 in Genesis 1, but land creatures were created on Day 6. Kosher food laws distinguish sea creatures by anatomy, and both set apart flying creatures by diet, but land creatures. These laws were not given to all humanity but to the Israelites through Moses in the Sainaitic Covenant. Originally, humans in the early part of Genesis were vegetarian, along with the other creatures (Genesis 1:29-30). After God flooded the world, the surviving humans were told they could eat any meat they wanted as long as they didn’t drain the blood (Genesis 9:3-4). These laws were given to the Israelites to set the Jews apart from Gentiles. In the New Testament, these laws are not given to the Church, since they were never given to Gentiles as moral laws. Jesus said that what we eat doesn’t defile us, but rather what is in our hearts is what defiles us (Matt 15:10-20). Paul repeats this idea in Romans 14, when discussing vegetarianism, and in 1 Corinthians 8-10, when addressing the consumption of idol meat. These things don’t determine how holy a person is; rather, it is their behavior that will be judged.
Resources:
BioExplorer – top 10 Poisonous Birds
Mental Floss – Poisonous Birds
Toxic Mammals
Quail poison (Coturnism)
Quail is Kosher