Daf Yomi Shabbos 48 Amud Aleph

Studying Shabbos Perek Revii, Mem Ches.

Interesting case involving an eved of the exilarch.... he put a cold water kettle on top of a hot water kettle on Shabbos.... if you read the loshon of the gemarah, the Rabbis who were visiting the exilarch had an absolute cow!

Okay, so we can put hot on hot, but not cold on hot. Why? Because we can insulate already hot things, but we can't heat things that aren't hot on Shabbos.

Good stuff.

There is also debate on whether riding a horse on Shabbos is breaking Shabbos since the principle of "a living thing supports its own weight" would apply.