لَوْ خَرَجُوْا فِيْكُمْ مَّا زَادُوْكُمْ اِلَّا خَبَالًا وَّلَاَوْضَعُوْا خِلٰلَكُمْ يَبْغُوْنَكُمُ الْفِتْنَةَۚ وَفِيْكُمْ سَمّٰعُوْنَ لَهُمْۗ وَاللّٰهُ عَلِيْمٌۢ بِالظّٰلِمِيْنَ ( التوبة: ٤٧ )
Law kharajoo feekum maa zaadookum ilaa Khabaalanw wa la awda'oo khilaalakum yabghoona kumul fitnata wa feekum sammaa'oona lahum; wallaahu 'aleemum biz zaalimeen (at-Tawbah 9:47)
Had they gone forth with you, they would not have increased you except in confusion, and they would have been active among you, seeking [to cause] you fitnah [i.e., chaos and dissension]. And among you are avid listeners to them. And Allah is Knowing of the wrongdoers. (At-Tawbah  : 47)
1 Mufti Taqi Usmani
And had they set out with you, they would have added nothing for you but trouble, and would have run around in your midst seeking mischief against you. Still, among you there are those who spy for them. Allah is aware of the wrongdoers.