The Holy Quran

وَأَقْسَمُواْ بِاللّهِ جَهْدَ أَيْمَانِهِمْ لَئِن جَاءتْهُمْ آيَةٌ لَّيُؤْمِنُنَّ بِهَا قُلْ إِنَّمَا الآيَاتُ عِندَ اللّهِ وَمَا يُشْعِرُكُمْ أَنَّهَا إِذَا جَاءتْ لاَ يُؤْمِنُونَ

And they swear a solemn oath by Allah that if there come unto them a portent they will believe therein. Say: Portents are with Allah and (so is) that which telleth you that if such came unto them they would not believe.