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.
The Saheeh International Quran Translation
وَلَقَدْ كَانُوا۟ عَٰهَدُوا۟ ٱللَّهَ مِن قَبْلُ لَا يُوَلُّونَ ٱلْأَدْبَٰرَ وَكَانَ عَهْدُ ٱللَّهِ مَسْـُٔولًاAnd 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.