وَلَقَدْ كَانُوا۟ عَـٰهَدُوا۟ ٱللَّهَ مِن قَبْلُ لَا يُوَلُّونَ ٱلْأَدْبَـٰرَ ۚ وَكَانَ عَهْدُ ٱللَّهِ مَسْـُٔولًا
Wa laqad kaanoo 'aahadul laaha min qablu laa yuwal loonal adbaar; wa kaana 'ahdul laahi mas'oolaa
Yet they had already promised God that they would not turn tail and flee, and a promise to God will be answered for.
They had already pledged to God that they would not turn their backs in flight — and a pledge to God will be asked about.