Quran 8:19

إِن تَسۡتَفۡتِحُواْ فَقَدۡ جَآءَڪُمُ ٱلۡفَتۡحُ‌ۖ وَإِن تَنتَہُواْ فَهُوَ خَيۡرٌ۬ لَّكُمۡ‌ۖ وَإِن تَعُودُواْ نَعُدۡ وَلَن تُغۡنِىَ عَنكُمۡ فِئَتُكُمۡ شَيۡـًٔ۬ا وَلَوۡ كَثُرَتۡ وَأَنَّ ٱللَّهَ مَعَ ٱلۡمُؤۡمِنِينَ ١٩

You sought victory (O disbelievers), and victory did come (it belonged to the believers). If you refrain (from aggression) it would be better for you, but if you return, so will we. Your armies will never help you, no matter how great the numbers. For ALLAH is on the side of the believers.