Is it Permissible to Eat Fish Cooked in Milk?

We learn in Tractate Chullin (page 103b): "All meat is forbidden to be cooked in milk, except for fish and locust meat". It is thus clear that according to the basic law, the prohibition of cooking and eating meat and milk does not include cooking fish with milk, because fish meat is not included in the 'meat' that the Torah prohibited, and is not even prohibited by rabbinic decree. However, Maran the Beit Yosef (in section 87) wrote that one should nevertheless not eat fish with milk because of danger. The Levush wrote similarly. Rabbi Yaakov Tzahalon, the wise physician, also wrote that one should not eat fish with milk because it causes illness.

Nevertheless, many authorities ruled leniently regarding eating fish with milk, and the Rema in his work Darkei Moshe wrote that he had not seen people being careful about this. Some authorities, including Maran the Chida, wrote that even Maran the Beit Yosef did not intend to prohibit eating fish with milk, but rather eating fish with meat, and what was written in the Beit Yosef about fish with milk was a scribal error (meaning a printing error). Therefore, although we generally rule according to Maran the Beit Yosef, in this case there is room to be lenient even initially.

The Gaon Rabbi Shalom Messas z"l wrote to be completely lenient in this matter, because it is not at all clear that Maran of the Shulchan Aruch prohibited eating fish with milk, and also because the custom of several Sephardic communities was to be lenient about eating fish with milk. Modern physicians agree that there is no concern of serious illness from eating fish with milk.

Maran Rabbi Ovadia Yosef shlit"a explains that the Sephardic custom was to prohibit eating fish with milk due to concern of danger, and several authorities explicitly wrote that the Sephardic custom is to be stringent in this matter. It is very difficult to believe that it is a scribal error in the Beit Yosef book, because such a custom to prohibit would not have spread with the agreement of the great rabbis of the generations if the entire source of the law was a complete error stemming from a scribal mistake. Certainly, if it were an error, the great rabbis of the generation at the time of Maran and those close to that time would have made known their opinion that there was an error in the Beit Yosef book. Especially since Maran himself proofread his book and did not comment anything about this. Several authorities ruled to prohibit based on the custom, including the Gaon Rabbeinu Yosef Chaim in the book 'Ben Ish Chai'.

Therefore, it is appropriate to be stringent initially not to eat fish with milk, but if fish was already cooked with milk, one may eat it even for Sephardim who customarily avoid it.

Nevertheless, regarding eating fish with butter (which is not like actual milk), several authorities wrote to be lenient even according to the Sephardic custom, and so wrote the Gaon Rabbi Abdullah Somekh z"l from Baghdad, that the custom in his city was to permit frying fish with butter. Therefore, those who are accustomed to eating fish with butter may maintain their custom (and there is room to be lenient also with cream from which butter is produced). Those of Ashkenazi descent customarily permit all of this completely and may maintain their custom.

Rulings of Rabbi Ovadia Yosef shlit"a courtesy of the "Daily Halacha" website