Say, "I only advise you of one [thing] - that you stand for Allah, [seeking truth] in pairs and individually, and then give thought." There is not in your companion any madness. He is only a warner to you before a severe punishment.
The Saheeh International Quran Translation
قُلْ إِنَّمَآ أَعِظُكُم بِوَٰحِدَةٍ أَن تَقُومُوا۟ لِلَّهِ مَثْنَىٰ وَفُرَٰدَىٰ ثُمَّ تَتَفَكَّرُوا۟ مَا بِصَاحِبِكُم مِّن جِنَّةٍ إِنْ هُوَ إِلَّا نَذِيرٌ لَّكُم بَيْنَ يَدَىْ عَذَابٍ شَدِيدٍSay, "I only advise you of one [thing] - that you stand for Allah, [seeking truth] in pairs and individually, and then give thought." There is not in your companion any madness. He is only a warner to you before a severe punishment.