Walaqad kanoo AAahadoo Allaha min qablu la yuwalloona aladbara wakana AAahdu Allahi masoolan
English
Ahmed Ali
Whereas earlier they had made a promise to God that they would never turn their backs; and a promise made to God is answerable.
15
Tafseer
'Abdullāh Ibn 'Abbās / Muḥammad al-Fīrūzabādī
تفسير : (and verily they had already sworn unto allah) before the battle of the ditch, on the occasion of the battle of the clans (that they would not turn their backs) fleeing from the idolaters. (an oath to allah) the one who breaks his oath to allah (must he answered for) will be asked about it on the day of judgement.
Jalāl al-Dīn al-Maḥallī
تفسير : though they had assuredly pledged to god before that, that they would not turn their backs [to flee]; and a pledge given to god must be answered for, regarding whether it was fulfilled [or not].