﴿ 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”

(And they swear a solemn oath) an utmost oath, for when one swears by Allah, one swears a solemn oath (by Allah that if there come unto them a portent) as they have asked (they will believe therein) they will believe in that sign. (Say) O Muhammad, to those who sneer and their folk: (Portents are with Allah) the signs come from Allah (and (so is) that which telleth you) and how do you know, O believers (that if such) the signs (came unto them they would not believe) by Allah they will not believe in the sign.