وَلَئِنۡ أَرۡسَلۡنَا رِيحٗا فَرَأَوۡهُ مُصۡفَرّٗا لَّظَلُّواْ مِنۢ بَعۡدِهِۦ يَكۡفُرُونَ ٥١
But if We should send a [bad] wind and they saw [their crops] turned yellow, they would remain thereafter disbelievers.1
Translation: Saheeh International (English)
1 Denying and ungrateful for the previous favors of Allāh.
Each word's meaning and sound
If we were to send upon their farms and crops a wind which would spoil them, and they were to then see their crops yellow in colour after they had previously been green, they would then begin to show ingratitude to the numerous other bounties of Allah they were given before that.
Al-Mukhtasar in interpreting the Noble Quran