807. Warming Cold Water

Shabbos 22:4

One may place a jug of water in front of the fire, not to warm it but to take the chill out of it. Similarly, one may place a flask of oil near a fire so that it will become room temperature but not for it to get warm. One may dip his hand in water or oil and warm it by the fire so long as the liquid on his hand does not get so hot that it would burn a baby’s stomach. On Shabbos, one may warm a cloth and place it on his abdomen.

Shabbos 22:5

It is not permitted to put cold water in a tub in a bathhouse full of hot water because this will cause the cold water to get quite hot. Similarly, one may not put a flask of oil in such a tub because that would be tantamount to cooking it. Conversely, it is permitted to put hot water into a tub of cold water.