﴿ إِلَّآ أَن يَشَآءَ ٱللَّهُ ۚ وَٱذْكُر رَّبَّكَ إِذَا نَسِيتَ وَقُلْ عَسَىٰٓ أَن يَهْدِيَنِ رَبِّى لِأَقْرَبَ مِنْ هَٰذَا رَشَدًۭا ﴾

“without (adding], "if God so wills." And if thou shouldst forget [thyself at the time, and become aware of it later], call thy Sustainer to mind and say: "I pray that my Sustainer guide me, even closer than this, to a consciousness of what is right!"”

According to the respective Quranic commentaries of Qatada and Mutrif ibn ‘Abdullah, the mention here of 300 years, or 309 years, is only a report of what people said and not information from God. On the basis of unauthentic stories, the people of the Book of those days used to believe that the period of stay of the ‘Men of the Cave’ in the cave was 300 years, according to the solar calendar, or 309 years according to the lunar calendar. (Tafsir ibn Kathir, vol. 3, p. 79 ). The Quran has merely reported this popular view, but at the same time has rejected it as baseless, saying, ‘God knows best how long they stayed in it.’ The researchers of the present age have discovered that, according to the solar calendar, this period was of 196 years. This discovery proves that the Quran is the book revealed by God, who is aware of all past and future happenings, and that because of this knowledge He did not accept the aforesaid belief. Had the Quran been the product of human effort, it would have adopted the most popular belief prevalent at that time, which would have ultimately clashed with the findings of subsequent research.