Tafsir of the verse:

ﺍﻟﻠﻪ ﻳﺘﻮﻓﻰ ﺍﻷﻧﻔﺲ ﺣﻴﻦ ﻣﻮﺗﻬﺎ ﻭﺍﻟﺘﻲ ﻟﻢ ﺗﻤﺖ ﻓﻲ ﻣﻨﺎﻣﻬﺎ ﻓﻴﻤﺴﻚ ﺍﻟﺘﻲ ﻗﻀﻰ ﻋﻠﻴﻬﺎ ﺍﻟﻤﻮﺕ ﻭﻳﺮﺳﻞ ﺍﻷﺧﺮﻯ ﺇﻟﻰ ﺃﺟﻞ ﻣﺴﻤّﻰ ﺇﻥ ﻓﻲ ﺫﻟﻚ ﻵﻳﺎﺕ ﻟﻘﻮﻡ ﻳﺘﻔﻜﺮﻭﻥ
http://al-Quran.info/39/42/N8

Four of the states on human body:

1) Death mode
2) Sleep mode
3) Dream mode
4) Awake mode

♦ Death mode:

There are many types of Ruh/Spirits. Angel of death detaches the Ruh-e-insani (nafs/soul) from human body at the time of death and if he puts Ruh-e-Jamadi (glacial/geological spirit, the type of Ruh that keeps the dead body free from decomposition) in it so it does not decompose https://en.wikipedia.org/wiki/Incorruptibility and if he does not put that Ruh, then the body decomposes https://www.aftermath.com/content/human-decomposition

It is not that only the bodies of saints are not decomposed https://mastodon.social/@Quraniverse/100398105615191489

Normally every body decomposes after death except if remained intact http://www.yourdictionary.com/paranormally

♦ Sleep mode:

What is sleep and why it comes?

Simply a rest mode. To give the rest to whole human body, the Angel of sleep detaches the Ruh-e-insani (nafs/soul) and puts Ruh-e-Nabati (botonical spirit, the type of Ruh that maintains oxygen and growth in the body during sleep) so that the sleeping human body remains intact and breaths and grows like plants.

♦ Dream mode:

During the sleep mode, Ruh-e-Insani (soul or nafs) is kept in the realm of unseen from where it is sometimes telepathically connected to/with Ruh-e-Nabati because of which the state comes on human body that is called "Dreams".

♦ Awake mode:

When the Angel detaches the Ruh-e-Nabati from the sleeping human body and puts back the Ruh-e-insani in it so a person becomes awake.