Hud
فَلَعَلَّكَ تَارِكٌۢ بَعْضَ مَا يُوحَىٰٓ إِلَيْكَ وَضَآئِقٌۢ بِهِۦ صَدْرُكَ أَن يَقُولُوا۟ لَوْلَآ أُنزِلَ عَلَيْهِ كَنزٌ أَوْ جَآءَ مَعَهُۥ مَلَكٌ ۚ إِنَّمَآ أَنتَ نَذِيرٌ ۚ وَٱللَّهُ عَلَىٰ كُلِّ شَىْءٍ وَكِيلٌ
Then would you possibly leave [out] some of what is revealed to you, or is your breast constrained by it because they say, "Why has there not been sent down to him a treasure or come with him an angel?" But you are only a warner. And Allah is Disposer of all things.
Nearby ayahs help place verse 11:12 in sequence and meaning.
وَلَئِنْ أَذَقْنَـٰهُ نَعْمَآءَ بَعْدَ ضَرَّآءَ مَسَّتْهُ لَيَقُولَنَّ ذَهَبَ ٱلسَّيِّـَٔاتُ عَنِّىٓ ۚ إِنَّهُۥ لَفَرِحٌ فَخُورٌ
But if We give him a taste of favor after hardship has touched him, he will surely say, "Bad times have left me." Indeed, he is exultant and boastful -
إِلَّا ٱلَّذِينَ صَبَرُوا۟ وَعَمِلُوا۟ ٱلصَّـٰلِحَـٰتِ أُو۟لَـٰٓئِكَ لَهُم مَّغْفِرَةٌ وَأَجْرٌ كَبِيرٌ
Except for those who are patient and do righteous deeds; those will have forgiveness and great reward.
أَمْ يَقُولُونَ ٱفْتَرَىٰهُ ۖ قُلْ فَأْتُوا۟ بِعَشْرِ سُوَرٍ مِّثْلِهِۦ مُفْتَرَيَـٰتٍ وَٱدْعُوا۟ مَنِ ٱسْتَطَعْتُم مِّن دُونِ ٱللَّهِ إِن كُنتُمْ صَـٰدِقِينَ
Or do they say, "He invented it"? Say, "Then bring ten surahs like it that have been invented and call upon [for assistance] whomever you can besides Allah, if you should be truthful."
فَإِلَّمْ يَسْتَجِيبُوا۟ لَكُمْ فَٱعْلَمُوٓا۟ أَنَّمَآ أُنزِلَ بِعِلْمِ ٱللَّهِ وَأَن لَّآ إِلَـٰهَ إِلَّا هُوَ ۖ فَهَلْ أَنتُم مُّسْلِمُونَ
And if they do not respond to you - then know that the Qur'an was revealed with the knowledge of Allah and that there is no deity except Him. Then, would you [not] be Muslims?