Holy Quran » AL AHZAB : 15

And they had already promised Allah before not to turn their backs and flee. And ever is the promise to Allah [that about which one will be] questioned.

{ ولقد كانوا عاهدوا الله من قبل لا يولون الأدبار وكان عهد الله مسؤولا} عن الوفاء به.