Yusuf Ali
In the thought that some back-breaking calamity was about to be inflicted on them;

Sahih International
Expecting that there will be done to them [something] backbreaking.

Shakir
Knowing that there will be made to befall them some great calamity.

Pickthall
Thou wilt know that some great disaster is about to fall on them.

محمد جالندھری
خیال کریں گے کہ ان پر مصیبت واقع ہونے کو ہے