Fish & Meat
The Shulchan Arukh states that we need to be careful not to eat meat and fish together, because it carries a danger of "tzaraat" an affliction of the skin mentioned in the Torah (YD 116:2). The source is the gemara in Pesachim (76b), which states that fish that are roasted together with meat can't be eaten with milk, because even though there is no contact between the two foods in roasting, the fish do absorb some of the taste of the meat and so this transgresses the separation of meat and milk. The passage continues, "Mar bar Rav Ashi said, it is forbidden even in salt [the usual way of eating fish] because it carries a danger of odor and 'something else'". Rashi and other commentaries explain that this unmentionable 'something else' is tzaraat.
In a number of past columns we have discussed the nature of the prohibition of milk and meat and the difference between kosher animals and kosher fish.
In brief, the kosher animals have a neutral animal nature which can be elevated to G-d's service, which is represented by the meat. They also have a lower, completely bestial animal nature which has to be purged, repre- sented by the blood. We see that in the Mikdash the blood is dashed on the side of the altar or poured out at the base, whereas the meat is offered to HaShem on the altar fire.
Koshered meat is separated from its lower nature by slaughter and by the draining and salting out of the blood. Milk is elevated from its source in the blood by being transformed into a completely new substance. The red blood is transformed into white milk, reminding us of the verse from Yishayahu (1:18), "Even if your sins are red, they will be white as snow". When they come together, these separations are weakened; the meat comes back into contact with blood, albeit transformed blood; the milk is transported back into its original carnal substrate.
Whereas meat and milk represent separation from our animal nature, as shown by the distancing from the blood, fish, which do not require slaughter or salting, represent the elevation of our animal nature. They live in a completely altered environment, the sea, representing Torah or pure kindness. In that rarefied environment, free from our wicked inclinations and the "evil eye", even our bodily desires and functions are elevated and acceptable to HaShem. That is why fish are especially appropriate to Shabbat, which also represents the elevation and perfection of our material nature.
This entire construct focuses on our lower material nature seen as the source of base appetites, or taava. However, this approach will not help us understand the prohibition of fish and meat. The plague of tzaraat is specifically related not to "ritual" prohibitions but rather to interpersonal ones. The most well-known is that slander can lead to tzaraat as explained in Rashi on Shemot 4:6. But the gemara in Arkhin (16b) counts seven different transgressions which can lead to tzaraat; all of these are interpersonal transgressions such as stealing or pride, or else transgressions which are direct insults to the Creator, such as blasphemy or false oaths. None of the seven are merely "ritual" transgressions. Maharal on this passage points out that the Torah states that one afflicted with tzaraat is compelled to sit isolated away from the camp (Vayikra 13:46); he explains that since the one afflicted with tzaraat interfered with harmony among others, he is obligated now to isolate himself from them (Chidushei Aggadot).
Fortunately, there is an additional halachic distinction between meat and fish which does relate particularly to this interpersonal aspect of the Torah. All kosher species of animal are docile grazers; they all begin with good "midot", or personalities. None are aggressive; none are violent carnivores; none are scavengers. In other words, we start out with species with good "interpersonal" qualities; what is left is merely the lower bestial tendency to indulgence, which is treated by slaughter and the draining and salting of blood.
This limitation does not apply to kosher fish. Among the vast number of kosher fish species we find herbivores, carni- vores and even scavengers. Some of our fish friends come with very unpalat- able midot!
It seems that just as our lower animal nature can be elevated by Torah, so can our baser personality traits, though this is certainly much more difficult. For instance, we find in the gemara that Torah scholars may occasionally be called upon to be angry or callous (Taanit 4a), or even vindictive (Yoma 23a) in defense of the Torah. To the best of my knowledge none of these traits are ever praised by our sages with regard to someone who is not a talmid chacham.
However, these traits can only be kosher if they are completely sub- merged in the sea of Torah, without the slightest admixture of concern for personal pride or status. When the slightest bit of personal concern is absorbed, then these qualities are totally destructive, making a person detestable (the :"odor" mentioned in the gemara in Pesachim) and abhorrent (tzaraat). This is symbolism of the fish, coming from the sea (likened to the sea of Torah) absorbing even the slightest whiff of meat, even through roasting.
It is interesting to note that the gemara does not state that the meat is forbidden - only the fish. This is logical according to our approach, because the meat is in the first place acceptable from the point of view of its "inter- personal" qualities, coming as it does from a docile kosher species. (However, halachically there is no difference between the fish and the meat.)