The mishna has a group of materials are forbidden to use for insulation only when they are moist. When they are moist, they add heat, but when they’re dry, it’s muttar bc they don’t add heat. ( straw grape skins grasses or fibers) The gemara in unsure if this is only when they’re naturally moist or even externally moist

Fruits and clothing can be used or insulation. (Dispute beteeen mishna and braisa if they are ok if moist). Dove feathers, sawdust, splinters form flax combings are all ok.

There a story about Elisha who risked his life to wear Tefillin when it was outlawed by the romans. He lied and said his Tefillin were dove feathers and they miraculously appeared that way. The jewish people are compared to a dove and are only protected through mitzvos.

Hides are acceptable for insulation and are not muktzeh bc they are fit to lie on. The Gemara has a dispute whether this is only for an ordinary person who might use the hides to lie on, or even for a professional leather maker. Perhaps for the אומן it is muktzeh bc they wouldn’t want to mess it up.

Cotton shearings are ok for insulation but they are muktzeh. This presents a challenge when opening the pot to take out food. The shearings cannot be moved directly;rather, one picks up the lid of the pot and shakes off the shearings.

The number 39 melochos is based off the 39 activities of labor performed in the mishkan. Additionally the gemara mentions that the word מלאכה appears 39 times in the Torah.

It says Yosef came to the house (of potifar) to do his “work.” It’s a dispute in the gemara if this is literal or a euphemism for sexual activity, meaning he was planning on sleeping with potifars wife.