وَيَقُولُ ٱلَّذِينَ كَفَرُوا۟ لَوْلَآ أُنزِلَ عَلَيْهِ ءَايَةٌ مِّن رَّبِّهِۦٓ ۗ إِنَّمَآ أَنتَ مُنذِرٌ ۖ وَلِكُلِّ قَوْمٍ هَادٍ
Wa yaqoolul lazeena kafaroo law laaa unzila 'alaihi Aayatum mir Rabbih; innamaaa anta munzirunw wa likulli qawmin haad
The disbelievers say, ‘Why has no miracle been sent down to him from his Lord?’ But you are only there to give warning: [earlier] communities each had their guide.
Those who deny say, "Why has no sign been sent down to him from his Lord?" You are only a warner, and for every people there is a guide.
Those asking want a miracle, and the reply turns to the messenger's role rather than to the sign: his work is warning, while guidance is something God has always supplied. The identity of the guide is unsettled: commentators propose the Prophet, or God, or someone raised up in each nation, and no other verse carries the phrase, so nothing outside it decides between them. Every reading still leaves no people unprovided for.