﴿ فَضَرَبْنَا عَلَىٰٓ ءَاذَانِهِمْ فِى ٱلْكَهْفِ سِنِينَ عَدَدًۭا ﴾

“And thereupon We veiled their ears in the cave for many a year,”

(Then We sealed up their hearing) We cast sleep over them, such that they slept (in the Cave for a number of years) 309 years.