Q. Re- question (3975) above that one of the actions mentioned by Talmud Horios (13b) that causes forgetfulness of Torah learning is using one’s clothes as a pillow and laying one’s head on them.
Is it permitted for one to sleep on a pillow that is covering an underneath pajamas?
How about sleeping with a Kipa that as one lays down and puts his head over a pillow, often separates from the head and one is laying over it. Is that permitted?
A. Mishna Berura (2: 2) mentions that if one places something that separates between his head and the piece of clothing it is possible that there is no concern of forgetting one’s learning.
Horav Shlomo Miller’s Shlit’a opinion is that concerning a Kipa or Kap’l, it is not seen as a separate piece of clothing, but just a something one is wearing, and is similar to laying on the sleeves of one’s jacket or shirt, that we mentioned as permitted.
Rabbi A. Bartfeld as revised by Horav Dovid Pam, Horav Aharon Miller and Horav Chanoch Ehrentreu Shlit’a.