What About The Pot?
‘Fish That Was Served On A [Meat] Plate…’
The Gemara (Pesachim 76a) writes that meat may not be eaten with fish due to danger, and chamira sakanta me’isura – we are more stringent with danger than prohibitions.
Shmuel, on our daf, asserts that hot fish placed on a (clean) meat plate may be eaten afterwards with a milk sauce. Even though the plate previously had hot meat on it and thus absorbed its flavor, the fish may be eaten with a milk sauce since it did not absorb the meat flavor directly from the meat.
Ab Initio or Post Initio?
The Rivan (Tosafos s.v. “hilch’sa”) citing, his father-in-law, Rashi, states that the fish may only be eaten with a milk sauce if it was cooked in a parve pot. The Rema (Yoreh De’ah 95:2) rules that parve food cooked in a meat pot should never be mixed with milk.
He rules leniently, though, if the pot was not used to cook meat within the previous 24 hours (i.e., it is not ben yomo – lit., “of that day”). In such a situation, the meat flavor absorbed in the vessel’s walls is considered pagum (rancid), so there is no problem.
The Gra (Yoreh De’ah 95:10) indicates similarly that one may cook fish in a non-ben yomo meat pot le’chatchilah – even if his intent is to eat it with milk. The Chachmas Adam (48:2), however, disagrees and writes that it is not permitted to do so le’chatchilah if one plans on eating the fish with milk. Everyone, though, agrees that one may eat the fish with milk once it has been cooked.
What Degree Danger?
The Maharshal (Yam Shel Shlomo, siman 15) indicates that, due to danger, one should refrain from eating fish cooked in a meat pot (even if it is clean and has not been used for at least 24 hours) because the fish absorbs the flavor of the meat that was cooked in the pot earlier. The Tur (cited by Chachmas Adam, topic 68:1) notes that some meticulous individuals designate separate pots to be used exclusively for fish and also refrain from eating fish on meat plates.
The author of sefer Issur V’Heter (topic 39), however, cites our Gemara as proof that it is only dangerous to eat fish with actual meat. Eating fish cooked in a clean meat pot (not used for 24 hours) does not pose a problem and may be served on either meat or dairy dishes.