Tafsir of Al-Furqan 25:11

بل كذبوا بالساعة

Nay, they deny the Hour, means, they say this in stubborn disbelief, not because they are seeking insight and guidance, but because their disbelief in the Day of Resurrection makes them say what they say.

وأعتدنا

And We have prepared, means, `We have made ready,'

لمن كذب بالساعة سعيرا

for those who deny the Hour, a flaming Fire. means, an unbearably hot and painful torment in the fire of Hell