Yusuf Ali
Were they to see a piece of the sky falling (on them), they would (only) say: "Clouds gathered in heaps!"

Sahih International
And if they were to see a fragment from the sky falling, they would say, "[It is merely] clouds heaped up."

Shakir
And if they should see a portion of the heaven coming down, they would say: Piled up clouds.

Pickthall
And if they were to see a fragment of the heaven falling, they would say: A heap of clouds.

محمد جالندھری
اور اگر یہ آسمان سے (عذاب) کا کوئی ٹکڑا گرتا ہوا دیکھیں تو کہیں کہ یہ گاڑھا بادل ہے