Jonah
أَمْ يَقُولُونَ ٱفْتَرَىٰهُ ۖ قُلْ فَأْتُوا۟ بِسُورَةٍ مِّثْلِهِۦ وَٱدْعُوا۟ مَنِ ٱسْتَطَعْتُم مِّن دُونِ ٱللَّهِ إِن كُنتُمْ صَـٰدِقِينَ
Or do they say [about the Prophet], "He invented it?" Say, "Then bring forth a surah like it and call upon [for assistance] whomever you can besides Allah, if you should be truthful."
Nearby ayahs help place verse 10:38 in sequence and meaning.
وَمَا يَتَّبِعُ أَكْثَرُهُمْ إِلَّا ظَنًّا ۚ إِنَّ ٱلظَّنَّ لَا يُغْنِى مِنَ ٱلْحَقِّ شَيْـًٔا ۚ إِنَّ ٱللَّهَ عَلِيمٌۢ بِمَا يَفْعَلُونَ
And most of them follow not except assumption. Indeed, assumption avails not against the truth at all. Indeed, Allah is Knowing of what they do.
وَمَا كَانَ هَـٰذَا ٱلْقُرْءَانُ أَن يُفْتَرَىٰ مِن دُونِ ٱللَّهِ وَلَـٰكِن تَصْدِيقَ ٱلَّذِى بَيْنَ يَدَيْهِ وَتَفْصِيلَ ٱلْكِتَـٰبِ لَا رَيْبَ فِيهِ مِن رَّبِّ ٱلْعَـٰلَمِينَ
And it was not [possible] for this Qur'an to be produced by other than Allah, but [it is] a confirmation of what was before it and a detailed explanation of the [former] Scripture, about which there is no doubt, from the Lord of the worlds.
بَلْ كَذَّبُوا۟ بِمَا لَمْ يُحِيطُوا۟ بِعِلْمِهِۦ وَلَمَّا يَأْتِهِمْ تَأْوِيلُهُۥ ۚ كَذَٰلِكَ كَذَّبَ ٱلَّذِينَ مِن قَبْلِهِمْ ۖ فَٱنظُرْ كَيْفَ كَانَ عَـٰقِبَةُ ٱلظَّـٰلِمِينَ
Rather, they have denied that which they encompass not in knowledge and whose interpretation has not yet come to them. Thus did those before them deny. Then observe how was the end of the wrongdoers.
وَمِنْهُم مَّن يُؤْمِنُ بِهِۦ وَمِنْهُم مَّن لَّا يُؤْمِنُ بِهِۦ ۚ وَرَبُّكَ أَعْلَمُ بِٱلْمُفْسِدِينَ
And of them are those who believe in it, and of them are those who do not believe in it. And your Lord is most knowing of the corrupters