They are waiting for nothing except a single Cry, after which there will be no second Cry.14
14. That is, only a single blast of the torment will be enough to annihilate them; no other will be needed for the purpose. Another meaning of the sentence can be: After this they will get no more relief and no more respite.وَقَالُوۡا رَبَّنَا عَجِّلْ لَّنَا قِطَّنَا قَبۡلَ يَوۡمِ الۡحِسَابِ (38:16) They say: “Our Lord, hasten to us our share (of chastisement) before the Day of Reckoning.”15
15. That is, Allah’s torment will be so severe and terrible as mentioned above, but just consider the behavior of these foolish people. They are telling the Prophet mockingly: Do not put off our affairs till the Day of Reckoning with which you are threatening us, but settle our account just now.: Whatever punishment is to be inflicted on us should be inflicted immediately.اِصۡبِرۡ عَلٰى مَا يَقُوۡلُوۡنَ وَاذۡكُرۡ عَبۡدَنَا دَاوٗدَ ذَا الۡاَيۡدِۚ اِنَّـهٗۤ اَوَّابٌ (38:17) (O Prophet), bear with patience what they say,16 and call to mind Our servant David,17 who was endowed with great strength18 and who constantly turned (to Allah).
16. The allusion is to the absurd conversation of the disbelievers of Makkah, as narrated above, to the effect that the Prophet (peace be upon him) was a sorcerer and a liar, and to their objection whether he was the only fit person in the sight of Allah to be appointed as a Messenger, and to their some accusation that he had vested interest in preaching the doctrine of Tauhid to the people and not any religious mission.
17. “Remember Our servant David”. It would mean: There is a lesson in this story for these people. Or it would mean: The remembrance of this story will help you too, to have patience. As the narrative is meant to serve both purposes, comprehensive words have been used as contain both meanings. (For the story of the prophet David (peace be upon him), see (Surah Al-Baqarah, Ayat 251); (Surah Bani-Israil, Ayat 55); (Surah Al-Anbiya, Ayats 78-81); (Surah An-Naml, Ayat 15) and the E.Ns thereof, and (E.Ns 14 to 16 of Surah Saba).