Al-Baqarah - 2:24

فَإِن لَّمْ تَفْعَلُواْ وَلَن تَفْعَلُواْ فَاتَّقُواْ النَّارَ الَّتِي وَقُودُهَا النَّاسُ وَالْحِجَارَةُ أُعِدَّتْ لِلْكَافِرِينَ
[2:24]
But if you do (it) not and never shall you do (it), then be on your guard against the fire of which men and stones are the fuel; it is prepared for the unbelievers.
But if ye cannot- and of a surety ye cannot- then fear the Fire whose fuel is men and stones,- which is prepared for those who reject Faith.
And if ye do it not - and ye can never do it - then guard yourselves against the Fire prepared for disbelievers, whose fuel is of men and stones.