Sleeping on One's Back or Stomach

Hello,

It is indeed forbidden to sleep on one's back or stomach (see Mishnah Berurah 240:6). The prohibition against sleeping on the back is due to concern that a person's member may become aroused during sleep and be apparent to many, which is considered disgraceful (Rashi, Berakhot 13b, s.v. late. See also Rashi, Niddah 14a, s.v. afrikid). The prohibition against sleeping on the stomach is because it may lead to heating and undesirable thoughts.

Best regards,

Hillel Meirs