﴿ وَمِنْهُم مَّن يَسْتَمِعُ إِلَيْكَ ۖ وَجَعَلْنَا عَلَىٰ قُلُوبِهِمْ أَكِنَّةً أَن يَفْقَهُوهُ وَفِىٓ ءَاذَانِهِمْ وَقْرًۭا ۚ وَإِن يَرَوْا۟ كُلَّ ءَايَةٍۢ لَّا يُؤْمِنُوا۟ بِهَا ۚ حَتَّىٰٓ إِذَا جَآءُوكَ يُجَٰدِلُونَكَ يَقُولُ ٱلَّذِينَ كَفَرُوٓا۟ إِنْ هَٰذَآ إِلَّآ أَسَٰطِيرُ ٱلْأَوَّلِينَ ﴾

“And there are among them such as [seem to] listen to thee [O Prophet]: but over their hearts We have laid veils which prevent them from grasping the truth, and into their ears, deafness. And were they to see every sign [of the truth], they would still not believe in it-so much so that when they come unto thee to contend with thee, those who are bent on denying the truth say, "This is nothing but fables of ancient times!"”

Please check ayah 6:26 for complete tafsir.