﴿ وَأَقْسَمُوا۟ بِٱللَّهِ جَهْدَ أَيْمَٰنِهِمْ لَئِن جَآءَتْهُمْ ءَايَةٌۭ لَّيُؤْمِنُنَّ بِهَا ۚ قُلْ إِنَّمَا ٱلْءَايَٰتُ عِندَ ٱللَّهِ ۖ وَمَا يُشْعِرُكُمْ أَنَّهَآ إِذَا جَآءَتْ لَا يُؤْمِنُونَ ﴾

“Now they swear by God with their most solemn oaths that if a miracle were shown to them, they would indeed believe in this [divine writ]. Say: "Miracles are in the power of God alone." And for all you know, even if one should be shown to them, they would not believe”

They that is the disbelievers of Mecca have sworn by God the most earnest oaths that if there came to them a sign of what they requested they will believe in it. Say to them ‘Signs are only with God’ and He sends them down as and when He wills; I am but a warner. But what will make you realise? how would you know if they have believed if these signs did come to them? In other words you would not know this; truly when they come they will not believe because of what I already know a variant reading for lā yu’minūna ‘they will not believe’ has lā tu’minūna ‘you will not believe’ making the address to the disbelievers; another variant reading has annahā instead of innahā ‘that truly’ as meaning la‘alla ‘that perhaps’ or as governed by the preceding clause la’in jā’athum āyatun ‘if there came to them a sign’.