If those who disbelieved but knew the time when they will not (21:39)

﴿لَوْ يَعْلَمُ الَّذِينَ كَفَرُوا حِينَ لَا يَكُفُّونَ عَن وُجُوهِهِمُ النَّارَ وَلَا عَن ظُهُورِهِمْ وَلَا هُمْ يُنصَرُونَ﴾
[ الأنبياء: 39]

21:39 If those who disbelieved but knew the time when they will not avert the Fire from their faces or from their backs and they will not be aided...

If these disbelieving rejecters of the resurrection were to know of the time when they will not be able to turn the hellfire away from their faces and backs, they would not be so hasty in seeking it.
If only they were to know that there shall be no one to help relieve them of the punishment, and if only they were convinced of its reality, they would not be so hasty either.

If only those who disbelieved knew (the time) when they will not be able to ward off the Fire from their faces, nor from their backs; and they will not be helped.

phonetic Transliteration

Law yaAAlamu allatheena kafaroo heena la yakuffoona AAan wujoohihimu alnnara wala AAan thuhoorihim wala hum yunsaroona

Abdullah Yusuf Ali - Translation

If only the Unbelievers knew (the time) when they will not be able to ward off the fire from their faces, nor yet from their backs, and (when) no help can reach them!

Safi-ur-Rahman al-Mubarakpuri

If only those who disbelieved knew (the time) when they will not be able to ward off the Fire from their faces, nor from their backs, and they will not be helped.

Page 325 English transliteration