قُل إِنَّما أَعِظُكُم بِواحِدَةٍ ۖ أَن تَقوموا لِلَّهِ مَثنىٰ وَفُرادىٰ ثُمَّ تَتَفَكَّروا ۚ ما بِصاحِبِكُم مِن جِنَّةٍ ۚ إِن هُوَ إِلّا نَذيرٌ لَكُم بَينَ يَدَي عَذابٍ شَديدٍ

Say, “I only advise you on one matter: that you stand for God in pairs or individually, and then reflect. There is no insanity in your friend; he is only a warner to you before the onset of a severe punishment.”