Ar-Ra'd 13:14

لَهُۥ دَعْوَةُ ٱلْحَقِّ ۖ وَٱلَّذِينَ يَدْعُونَ مِن دُونِهِۦ لَا يَسْتَجِيبُونَ لَهُم بِشَىْءٍ إِلَّا كَبَٰسِطِ كَفَّيْهِ إِلَى ٱلْمَآءِ لِيَبْلُغَ فَاهُ وَمَا هُوَ بِبَٰلِغِهِۦ ۚ وَمَا دُعَآءُ ٱلْكَٰفِرِينَ إِلَّا فِى ضَلَٰلٍۢ

For Him (alone) is prayer in Truth: any others that they call upon besides Him hear them no more than if they were to stretch forth their hands for water to reach their mouths but it reaches them not: for the prayer of those without Faith is nothing but (futile) wandering (in the mind).