The Rabbis have taught that a small salt fish will cause death if partaken of after seven, seventeen, or twenty-seven days; some say after twenty-three days. This is said with reference to half-cooked fish, but when properly cooked there is no harm in it. Neither does any harm result from eating half-cooked fish, if strong drink be taken after it.
Berachoth, fol. 44, col. 2.