Woe, that Day, to those who deny.
meaning, when they come to the imprisonment, Allah threatened them with, on the Day of Judgement, and the disgraceful torment.
The statement, "Woe," has already been discussed previously and there is no need to repeat it here.
Basically, it means destruction and devastation. This is like what is said,
"Woe to so-and-so."
This is similar to what has been recorded in the Musnad and the Sunan collections on the authority of Bahz bin Hakim bin Mu`awiyah bin Haydah, who reported from his father, who reported from his grandfather that the Messenger of Allah said,
وَيْلٌ لِلَّذِي يُحَدِّثُ فَيَكْذِبُ لِيُضْحِكَ النَّاسَ
وَيْلٌ لَهُ
وَيْلٌ لَه
Woe unto whoever speaks, and lies in order to make the people laugh.
Woe unto him,
woe unto him.
Then Allah says, in explaining who are the wicked, disbelieving deniers,
الَّذِينَ يُكَذِّبُونَ بِيَوْمِ الدِّينِ