Surah Ar-Rum 30:51

وَلَئِنْ أَرْسَلْنَا رِيحًا فَرَأَوْهُ مُصْفَرًّا لَّظَلُّوا۟ مِنۢ بَعْدِهِۦ يَكْفُرُونَ

But if We should send a [bad] wind and they saw [their crops] turned yellow, they would remain thereafter disbelievers.

Translation: Saheeh International

Tafsir

But if wa-la-in the lām is for oaths We unleash a different wind that damages vegetation and they see it turn yellow they would begin la-zallū is the response to the conditional oath after that that is after its turning yellow to disbelieve to deny the grace of having been given rain.

Excerpt from Tafsir al-Jalalayn, commentary on 30:51, via Quran.com. The reader has the full commentary and 9 more tafsirs.