وَلَقَدْ كَانُواْ عَـٰهَدُواْ ٱللَّهَ مِن قَبْلُ لَا يُوَلُّونَ ٱلْأَدْبَـٰرَۚ وَكَانَ عَهْدُ ٱللَّهِ مَسْــُٔولاً ١٥
And verily they had already sworn unto Allah that they would not turn their backs (to the foe). An oath to Allah must be answered for.