A. Yusuf Ali:Translation:
It is Allah that takes the souls (of men) at
death; 4306 and those that die not (He takes) during
their sleep: 4307 those on whom He has passed the
decree of death, He keeps back 4308 (from returning
to life), but the rest He sends (to their bodies) for a
term appointed verily in this are Signs 4309 for those
who reflect.

Muhammad Asad:Translation:
It is God [alone that has this power - He] who causes all human beings to die at the time of their [bodily] death, and [causes to be as dead], during their sleep, those that have not yet died: 44 thus, He withholds [from life] those upon whom He has decreed death, and lets the others go free for a term set [by Him]. In [all] this, behold, there are messages indeed for people who think!
4306 The mystery of life and death, sleep and dreams, is a fascinating enigma, of which the solution is perhaps beyond the ken of man. A vast mass of superstition as well as imaginative and psychological literature has grown up about it. But the simplest and truest religious doctrine is laid down here in a few words. In death we surrender our physical life, but our soul does not die; it goes back to a plane of existence in which it is more conscious of the realities of the spiritual world: "Allah takes the soul".
4307 Cf. 6:60. What is sleep? As far as animal life is concerned, it is the cessation of the working of the nervous system, though other animal functions, such as digestion, growth, and the circulation of the blood, continue, possibly at a different pace. It is the repose of the nervous system, and in this respect it is common to man and animals, and perhaps even to plants, if, as is probable, plants have a nervous system. The mental processes (and certainly volition) are also suspended in sleep, except that in ordinary dreams there is a medley of recollections, which often present vividly to our consciousness things that do not or cannot happen in nature as we know it in our coordinated minds. But there is another kind of dream which is rarer-one in which the dreamer sees things as they actually happen, backwards or forwards in time, or in which gifted individuals see spiritual truths otherwise imperceptible to them. How can we explain this? It is suggested that our soul or personality-that something which is above our animal life-is then in a plane of spiritual existence akin to physical death (see last note), when we are nearer to Allah. In poetic imagery, Sleep is "twin-brother to Death".
4308 Sleep being twin-brother to Death, our souls are for the time being released from the bondage of the flesh. Allah takes them for the time being. If, as some do, we are to die peacefully in sleep, our soul does not come back to the physical body, and the latter decays and dies. If we still have some period of life to fulfil according to Allah's decree, our soul comes back to the body, and we resume our functions in this life.
4309 If we contemplate these things, we can see more clearly many spiritual truths: e.g. (1) that our bodily life and death are not the whole story of our existence; (2) that in our bodily life we may be dead to the spiritual world, and in our bodily death, may be our awakening to the spiritual world; (3) that our nighdy Sleep, besides performing the function of rest to our physical life, gives us a foretaste of what we call death, which does not end our personality; and (4) that the Resurrection is not more wonderful than our daily rising from Sleep, "twinbrother to Death".