Tafsir of Az-Zukhruf 43:66

The Resurrection will come suddenly, and Enmity will arise between close Friends among the Disbelievers Allah says,

هل ينظرون

Do they only wait `do these idolaters who disbelieve in the Messengers wait'

إﻻ الساعة أن تٲتيهم بغتة وهم ﻻ يشعرون

only for the Hour that it shall come upon them suddenly while they perceive not? means, for it is real and will inevitably come to pass, and these negligent people are unprepared for it. When it comes, it will catch them unawares, and on that Day they will feel the utmost regret when regret will not benefit them in the slightest and will not afford them any protection

اﻻخﻼأء يوميذ بعضهم لبعض عدو إﻻأ المتقين