التفسير التبليغي
(وَمَا كَانَ قَوْلَهُمْ إِلاَّ أَنْ قَالُوا رَبَّنَا اغْفِرْ لَنَا ذُنُوبَنَا وَإِسْرَافَنَا فِي أَمْرِنَا وَثَبِّتْ أَقْدَامَنَا وَانْصُرْنَا عَلَى الْقَوْمِ الْكَافِرِينَ)
This is an instruction from Allah Almighty to the believers on what they should do and say when encountering the enemy.
This is an admonition from Allah Almighty regarding the manner of seeking through supplications during calamities and tribulations.
It is as if what happened was a result of a previous sin, so they became aware of the cause (وَمَا كَانَ قَوْلُهُمْ إِلَّا أَنْ قَالُوا رَبَّنَا).
The people knew that sins and extravagance are among the greatest causes of failure.
(رَبَّنَا اغْفِرْ لَنَا ذُنُوبَنَا) Nothing afflicts us except by a sin of negligence that we committed.
All the worldly afflictions that descend are only due to the sins of mankind.
They had no other words besides these words.
In the midst of intense effort, in the thick of battle, their sole concern was forgiveness (رَبَّنَا اغْفِرْ لَنَا ذُنُوبَنَا وَإِسْرَافَنَا فِي أَمْرِنَا).
The greatest objective is the forgiveness of sins.
Sins delay victory and relief, so seeking forgiveness is obligatory before asking for triumph.
(وَمَا كَانَ قَوْلُهُمْ إِلَّا أَنْ قَالُوا) meaning: while they were striving to uphold the religion of Allah, (رَبَّنَا اغْفِرْ لَنَا ذُنُوبَنَا).
(وَإِسْرَافَنَا فِي أَمْرِنَا) Speak about your shortcomings!
What is meant by "extravagance in our affair" is a deficiency in effort.
What is meant by His saying: (أَمْرِنَا) is our religion, our obligations, and our bearing of responsibility.
(وَثَبِّتْ أَقْدَامَنَا) meaning: strengthen us in adherence to Your true religion and the effort of Your Prophet Muhammad, peace be upon him.
(وَثَبِّتْ أَقْدَامَنَا) through steadfastness, (وَانْصُرْنَا عَلَى الْقَوْمِ الْكَافِرِينَ) through striving.
Steadfastness of foot can only come from the steadfastness of its owner upon the effort in religion.
The thought of the Hereafter and certainty in Allah are the believer's aspiration.
Source: التفسير التبليغي