Quran 18:26 — The Cave (Al-Kahf)

قُلِ اللَّهُ أَعلَمُ بِما لَبِثوا ۖ لَهُ غَيبُ السَّمٰوٰتِ وَالأَرضِ ۖ أَبصِر بِهِ وَأَسمِع ۚ ما لَهُم مِن دونِهِ مِن وَلِىٍّ وَلا يُشرِكُ فى حُكمِهِ أَحَدًا

Say, "GOD is the best knower of how long they stayed there." He knows all secrets in the heavens and the earth. By His grace you can see; by His grace you can hear. There is none beside Him as Lord and Master, and He never permits any partners to share in His kingship.

[18:25] They stayed in their cave three hundred years, increased by nine.*

[18:27] You shall recite what is revealed to you of your Lord's scripture. Nothing shall abrogate His words, and you shall not find any other source beside it.