Al Ahzab Ayah 15

وَلَقَدْ كَانُواْ عَـٰهَدُواْ ٱللَّهَ مِن قَبْلُ لَا يُوَلُّونَ ٱلْأَدْبَـٰرَ‌ۚ وَكَانَ عَهْدُ ٱللَّهِ مَسْــُٔولاً ١٥ They had already pledged to Allah earlier never to turn their backs ?in retreat?. And a pledge to Allah must be answered for.