Proper Way of Sleeping

My friend told me that I should not sleep on my back. Is this true?

Shalom!

Thank you for your question.

Indeed, we are taught that one should not sleep in an “aparkid” position. It is not completely clear, however, what “aparkid” means! According to Rashi, (1) it means lying on one’s back, while according to one opinion cited in Tosfot, (2) it means lying on one’s stomach.

It is said that sleeping on one’s back can be embarrassing for a man,(3) and that sleeping on one’s stomach can lead to a seminal emission. As such, it is proper to comply with both interpretations and not sleep on one’s back or stomach. Instead, one should sleep on one’s side, (4) beginning with one’s left side and then switching sometime during the night to one’s right side. (5) Some authorities consider sleeping on one’s back or stomach to be so serious that they permit waking a sleeping person in order to have them turn onto their side, although le'halcha one shouldn't do so. (6) Sleeping on one’s back or stomach is only problematic for men while women may sleep any way they please.

Children should be educated in this halacha from the age of nine. (8)

On a related note, one should never sleep directly on the ground without some kind of interposition.(9) One should also never sleep with shoes on, as doing so is said to be “a taste of death.” (10) However, sleeping with shoes on is only a problem when sleeping in a bed or for an extended period of time. Many allow taking a nap on a recliner or falling asleep at a desk with shoes on. 

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