Allah T'ala says in the Holy Quran:

وَتَمَّتْ كَلِمَتُ رَبِّكَ صِدْقًا وَعَدْلاً لاَّ مُبَدِّلِ لِكَلِمَاتِهِ وَهُوَ السَّمِيعُ الْعَلِيمُ

وَإِن تُطِعْ أَكْثَرَ مَن فِي الأَرْضِ يُضِلُّوكَ عَن سَبِيلِ اللّهِ إِن يَتَّبِعُونَ إِلاَّ الظَّنَّ وَإِنْ هُمْ إِلاَّ يَخْرُصُونَ

إِنَّ رَبَّكَ هُوَ أَعْلَمُ مَن يَضِلُّ عَن سَبِيلِهِ وَهُوَ أَعْلَمُ بِالْمُهْتَدِينَ

006.115: The word of thy Lord does find its fulfilment in truth and in justice: None can change His words: for He is the one who hears and knows all.

006.116: Were you to follow the common run of those on earth, they will lead thee away from the way of Allah. They follow nothing but conjecture: they do nothing but lie.

006.117: Thy Lord knows best who strays from His way: He knows best who they are that receive His guidance.