لَوْ خَرَجُوا فِيكُم مَّا زَادُوكُمْ إِلَّا خَبَالًا وَلَأَوْضَعُوا خِلَالَكُمْ يَبْغُونَكُمُ الْفِتْنَةَ وَفِيكُمْ سَمَّاعُونَ لَهُمْ ۗ وَاللَّهُ عَلِيمٌ بِالظَّالِمِينَ
“Had they gone forth with you [believers], they would have been nothing but trouble for you, and would have scrambled around, seeking to spread discord in your midst. And some of you would have eagerly listened to them. And Allah has [perfect] knowledge of the wrongdoers.”
Part of the well-established hypocrites-who-stayed-behind-from-Tabuk passage of Surat al-Tawbah.