The #Quran indicates some resemblance between sleep & death. The Quran uses "Wafat" to describe death, & one of the verses states, 

"It is Allāh Who takes away the souls (Wafat) at the time of their death, & those that die not during their sleep. He keeps those (souls) for which He has ordained death & sends the rest for a term appointed. Verily, in this are signs for people who think deeply" (Q39:42)