[Wa qalalladhina kafaru a-idha kunna turaban wa aba'una] (And those who disbelieved say, "When we are dust, and our forefathers [likewise]...") as an interrogative. [A-inna lamukhrajun] (...shall we indeed be brought forth?) — meaning: shall we be resurrected? That is: we shall not be resurrected. This is an inquiry from them based on denial.
Muhammad said: The recitation of Nafi' (idha kunna) is with the kasrah of the alif as a declarative statement, and there is disagreement among the reciters regarding it. Whoever recites (a-idha) elides the ya', and does not make its pronunciation distinct.