Quran 48:22 from Surah Al-Fath on Divine Marvels.
وَلَوۡ قَٰتَلَكُمُ ٱلَّذِينَ كَفَرُواْ لَوَلَّوُاْ ٱلۡأَدۡبَٰرَ ثُمَّ لَا يَجِدُونَ وَلِيّٗا وَلَا نَصِيرٗا
English translation: And if fight you those who disbelieve surely they would turn the backs Then not they would find any protector and not any helper
Transliteration: walaw qatalakumu alladhina kafaru lawallawu al-adbara thumma la yajiduna waliyyan wala nasiran