﴿ وَإِمَّا نُرِيَنَّكَ بَعْضَ ٱلَّذِى نَعِدُهُمْ أَوْ نَتَوَفَّيَنَّكَ فَإِلَيْنَا مَرْجِعُهُمْ ثُمَّ ٱللَّهُ شَهِيدٌ عَلَىٰ مَا يَفْعَلُونَ ﴾

“And whether We show thee [in this world something of what We hold in store for those [deniers of the truth], or whether We cause thee to die [before that retribution takes place - know that, in the end], it is unto Us that they must return; and God is witness to all that they do.”

And whether wa-immā the nūn of the conditional particle in has been assimiliated with the extra mā We show you something of that which We promise them of chastisement during your lifetime the response to the conditional statement has been omitted in other words understand it as being fa-dhāka ‘then so shall it be’ or We take you to Us before punishing them to Us they shall return and God moreover is Witness Aware of what they do in the way of their denials and disbelief and so will chastise them with the severest punishment.