Sura al-Anʿām 6:109

وَأَقْسَمُوا۟ بِٱللَّـهِ جَهْدَ أَيْمَٰنِهِمْ لَئِن جَآءَتْهُمْ ءَايَةٌ لَّيُؤْمِنُنَّ بِهَا قُلْ إِنَّمَا ٱلْأَيَٰتُ عِندَ ٱللَّـهِ وَمَا يُشْعِرُكُمْ أَنَّهَآ إِذَا جَآءَتْ لَا يُؤْمِنُونَ

wa-aqsamū billāhi jahda aymānihim lain jāʾathum āyatun llayuminunna bihā qul innamā l-ayātu ʿinda allāhi wa-mā yushʿirukum annahā idhā jāʾat lā yuʾminūna

They swear their strongest oaths by Allah, that if a (special) sign came to them, by it they would believe. Say: "Certainly (all) signs are in the power of Allah: but what will make you (Muslims) realise that (even) if (special) signs came, they will not believe."?

Sura al-Kahf 18:19

وَكَذَٰلِكَ بَعَثْنَٰهُمْ لِيَتَسَآءَلُوا۟ بَيْنَهُمْ قَالَ قَآئِلٌ مِّنْهُمْ كَمْ لَبِثْتُمْ قَالُوا۟ لَبِثْنَا يَوْمًا أَوْ بَعْضَ يَوْمٍ قَالُوا۟ رَبُّكُمْ أَعْلَمُ بِمَا لَبِثْتُمْ فَٱبْعَثُوٓا۟ أَحَدَكُم بِوَرِقِكُمْ هَٰذِهِۦٓ إِلَى ٱلْمَدِينَةِ فَلْيَنظُرْ أَيُّهَآ أَزْكَىٰ طَعَامًا فَلْيَأْتِكُم بِرِزْقٍ مِّنْهُ وَلْيَتَلَطَّفْ وَلَا يُشْعِرَنَّ بِكُمْ أَحَدًا

wa-ka-dhālika baʿathnāhum li-yatasāʾalū baynahum qalā qāʾilun minhum kam labithtum qālū labithnā yawman aw baʿḍa yawmin qālū rabbukum aʿlamu bi-mā labithtum fa-ibʿathū aḥadakum bi-wariqikum hādhihi ilā l-madīnati fa-l-yanẓur ayyuhā azka ṭaʿāman fa-l-yaʾtikum birizqin minhu wa-l-yatalaṭṭaf wa-lā yushʿiranna bikum aḥadan

Such (being their state), we raised them up (from sleep), that they might question each other. Said one of them, "How long have ye stayed (here)?" They said, "We have stayed (perhaps) a day, or part of a day." (At length) they (all) said, "Allah (alone) knows best how long ye have stayed here.... Now send ye then one of you with this money of yours to the town: let him find out which is the best food (to be had) and bring some to you, that (ye may) satisfy your hunger therewith: And let him behave with care and courtesy, and let him not inform any one about you.