AND YET, if they [who refuse to see the truth] were to see part of the sky falling down, they would [only] say, [It is but] a mass of clouds!"

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

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

And if they were to see a portion of the heaven coming down, they would say: Piled-up clouds!

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