And if they were to see a fragment from the sky falling, (52:44)

Almuntakhab Fi Tafsir Alquran Alkarim

And if it so happens that they see a mass (sometimes devastating) falling from the sky, they would label it as a cumulus nimbus

Tafseer Tafheem-ul-Quran by Syed Abu-al-A'la Maududi

(52:44) (So obstinate are they that) even if they were to see some fragments of the sky falling down they would still say: 'It is only a mass of cloud.' *36

And if they were to see a fragment from the sky falling, meaning

*36) This is meant to expose the stubbornness of the Quraish chiefs, on the one hand, and to console the Holy Prophet (upon whom be peace) and his Companions, on the other. The Holy Prophet and his Companions wished that those people should be shown such a miracle by Allah as should convince them of the truth of his Prophet hood. At this, it has been said: Whatever miracle they might see with their eyes, they will in any case misinterpret it and invent an excuse for persisting in disbelief, for their hearts are not at all inclined to believe. At several other places also in the Qur'an their this stubbornness has been mentioned, e.g. in Surah Al-An`am: 111, it has been said: "Even if we had sent down the angels to them and made the dead speak with them and ranged all the things of the world before them (as a proof thereof), they would still have disbelieved," and in Surah AI-Hijr: 15: "Even if We had opened a gate for them in heaven, and they had begun w ascend through it during day time, they would have said: "Our eyes have been dazzled; nay, we have been bewitched."
 

And if they were to see a fragment from the sky falling, meaning in Urdu

یہ لوگ آسمان کے ٹکڑے بھی گرتے ہوئے دیکھ لیں تو کہیں گے یہ بادل ہیں جو امڈے چلے آ رہے ہیں