وَلَا يَزَالُ ٱلَّذِينَ كَفَرُوا۟ فِى مِرْيَةٍ مِّنْهُ حَتَّىٰ تَأْتِيَهُمُ ٱلسَّاعَةُ بَغْتَةً أَوْ يَأْتِيَهُمْ عَذَابُ يَوْمٍ عَقِيمٍ
Wa laa yazaalul lazeena kafaroo fee miryatim minhu hattaa taatiyahumus Saa'atu baghtatan aw yaatiyahum 'azaabu Yawmin 'aqeem
The disbelievers will remain in doubt about it until the Hour suddenly overpowers them or until torment descends on them on a Day devoid of all hope.
Those who deny will remain in doubt about it until the hour comes upon them suddenly, or the torment of a barren day overtakes them.
ʿAqīm is the word for barrenness in a person, and it describes a wind that carries no rain. Applied to a day, it has drawn three readings: a day with no night to follow it, a day empty of any good for them, or the day of Badr, which would place the threat in this life. The image is of something that arrives and yields nothing.