Surah 18:23
"And do not say of anything, ‘Surely I am going to do that tomorrow,’"
This expression is similar to the thought in James 4:13–15: “Instead, you ought to say, ‘If it is the Lord’s will, we will live and do this or that.’” Interestingly, the Quran puts this expression into a conversation within the story of the companions of the cave – which seems to be a version of a legend about Christian characters.
- from The Quran with Christian Commentary: A Guide to Understanding the Scripture of Islam