Surah Ar-Ra'd (The Thunder), Verse 14

لَهٗ دَعْوَةُ الْحَقِّ وَالَّذِیْنَ یَدْعُوْنَ مِنْ دُوْنِهٖ لَا یَسْتَجِیْبُوْنَ لَهُمْ بِشَیْءٍ اِلَّا كَبَاسِطِ كَفَّیْهِ اِلَی الْمَآءِ لِیَبْلُغَ فَاهُ وَمَا هُوَ بِبَالِغِهٖ وَمَا دُعَآءُ الْكٰفِرِیْنَ اِلَّا فِیْ ضَلٰلٍ ۟

Lahoo da'watul haqq; wallazeena yad'oona min doonihee laa yastajeeboona lahum bishai'in illaa kabaasiti kaffaihi ilal maaa'i liyablugha faahu wa maa huwa bibaalighih; wa maa du'aaa'ul kaafireena illaa fee dalaal

“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).”

Quran 13:14 (Yusuf Ali Translation)