(Ahsaab) 33 : 15
وَلَقَدْ كَانُوا عَاهَدُوا اللَّهَ مِنْ قَبْلُ لَا يُوَلُّونَ الْأَدْبَارَ ۚ وَكَانَ عَهْدُ اللَّهِ مَسْئُولًا
And surely they had made before a covenant with Allah that they wouldn’t turn back, and the covenant made with Allah will be questioned.
The hypocrites who had been defeated in the Uhd war had made a covenant with Lord Allah that they would never turn back from any war in the future. But the hypocrites who had the habit of breaking the covenant and pledge, on seeing the abundant number of confederates started to ask permission to turn back from the battlefield-Khandakh battle. It is told in verse 59: 13 that the hypocrites fear the believers who disclose openly the character of them than they fear Lord Allah. See explanation 2: 26-27; 3: 152-153; 7: 102.