Testing of believers through disbelief

وَقَالُوا۟ لَوْلَا نُزِّلَ عَلَيْهِ ءَايَةٌ مِّن رَّبِّهِۦ ۚ قُلْ إِنَّ ٱللَّهَ قَادِرٌ عَلَىٰٓ أَن يُنَزِّلَ ءَايَةً وَلَـٰكِنَّ أَكْثَرَهُمْ لَا يَعْلَمُونَ

And they say, "Why has a sign not been sent down to him from his Lord?" Say, "Indeed, Allāh is Able to send down a sign, but most of them do not know."