808. Cooling Hot Water

Shabbos 22:6

Once hot water has been removed from the urn, it is permitted to add cold water in order to make it lukewarm. It is permitted to add hot water to cold water or vice versa so long as the hot water is not in the vessel in which it was heated. If it is, it would raise the temperature of the cold water too much. Similarly, if a pot is boiling, it is not permitted to add place spices to it even after removing it from the fire. One may add salt because salt will only cook over a very large flame. If one pours food from a pot to a bowl, he may then add spices even if it is boiling because a second vessel is not hot enough to cook.

Shabbos 22:7

On Shabbos, one may not soak asafoetida (a resin from an herb called Ferula, imbibed for medicinal purposes) in hot or cold water but one may soak it in vinegar. If one drank asafoetida on Thursday and Friday, he may soak it in cold water on Shabbos, warm it in the sun, and then drink it. This is permitted out of the concern that he may become sick if he stops his regimen.