Siman 567

One who is observing a fast may taste a dish if it requires salt or spices, and he tastes and spits it out. He may taste up to the amount of a revi'it, provided that he spits it out. And even though the palate derives pleasure from this—nevertheless, there is no prohibition in the matter, for in a fast one accepts upon himself that eating and drinking shall not enter his intestines, but he did not accept upon himself the prohibition of pleasure. This is not comparable to one who vows against food, who is forbidden from tasting it. There is one who says that even if he intends for the pleasure of the palate—it is permitted when he spits it out (Magen Avraham subsection 1). And it is a wonder to say so. This applies only to an individual fast. However, on Tisha B'Av and Yom Kippur—it is forbidden, as they are complete public fasts. The other four fasts were treated regarding this matter like an individual fast. Regarding this, our teacher, the Rema, indeed writes that there are those who are stringent in every public fast, and such is our custom. Thus far his words. For it is reasonable to say that in an individual fast, in such a case, he did not accept it upon himself, but not so in a public fast.

And even in a private fast, some say that they did not permit a revi'it at one time, but rather little by little. And when one tastes the small amount – he should spit it out. And more than a revi'it, even throughout the entire day – is forbidden (ibid. subsection 4). For when one tastes a revi'it at one time – it is impossible that he will not swallow a small amount. And some say that it is permitted even a revi'it at one time, if he knows himself that he is able to restrain himself so that he tastes nothing. And the custom among us is that the woman who is cooking – licks a little with her tongue to know if it needs salt or not. And in such a case, it certainly appears that there is no concern.

One who is accustomed to rinsing his mouth in the morning on a public fast—it is not proper to do so, for it is likely that he will swallow into his throat. And it appears to me that this is when he brings the water deep into his mouth, and raises his mouth upward and gargles the water in his throat. But when he takes the water into his mouth and he stands stooped, and his intention is only to clean the teeth, and there is no concern that he will swallow into his throat—it is permitted, except on Tisha B'Av and Yom Kippur. But on a private fast it is permitted to rinse in his usual manner since he spits it out, and even if there is more than a revi'it of water, since he does not intend to taste and derives no pleasure at all from the water. Therefore, with other liquids—it is forbidden, for he derives pleasure from it. (Ibid. subsection 7, see there that he permits with vinegar. And in my humble opinion, there are those for whom vinegar is pleasant to their palate.)

Our teacher, the Rema, wrote that it is permitted to chew cinnamon sticks and other spices and sweet wood to moisten one's throat, and to spit it out, except on Yom Kippur when it is forbidden. Thus far his words. For since there is no moisture of water in this – we are not concerned about it, as it is nothing more than a mere scent (and the difficulty of the Magen Avraham, subsection 8, is settled). And the swallowing of saliva is nothing, even on Yom Kippur (ibid.). And it is not possible otherwise at all, for if not so, we would be required to stand and spit the entire day.