COMMENTARY on 17:51
A. Yusuf Ali:

Translation:
"Or created matter which, in your minds, is hardest (to be raised up),- (Yet shall you be raised up)!" then will they say: "Who will cause us to return?" Say: "He who created you first!" Then will they wag their heads towards you, 2235 and say, "When will that be?" Say, "May be it will be quite soon!
Commentary:

2235  The sceptic shifts his ground when he is cornered in argument. It is no longer tenable for him to say that it cannot happen or that there is no one who can bring him back to life and memory. He now gets shaky, and says, "Well, when is that going to happen?" The actual time no man can tell. Indeed that event will be on a plane in which there will be no Time. Our relative ideas of time and place will have been completely overthrown, and it will appear to us then, not that it has been postponed too long, but that it has come too soon! See the next verse and note.

 

Muhammad Asad:

Translation:
or any [other] substance which, to your minds, appears yet farther removed [from life]!" 58 And [if] thereupon they ask, "Who is it that will' bring us back [to life]?"-say thou: "He who has brought you into being in the first instance." And [if] thereupon they shake their heads at thee [in disbelief] and ask, "When shall this be?"-say thou: "It may well be soon,
Commentary:
58  Lit., "or any created matter which, in your hearts, appears yet more difficult" - i.e., even less susceptible of having or receiving life.