﴿ يَٰٓأَيُّهَا ٱلَّذِينَ ءَامَنُوا۟ خُذُوا۟ حِذْرَكُمْ فَٱنفِرُوا۟ ثُبَاتٍ أَوِ ٱنفِرُوا۟ جَمِيعًۭا ﴾

“O YOU who have attained to faith! Be fully prepared against danger, whether you go to war in small groups or all together.”

Knowing that they went out to fight in the way of Allah, Allah said: (O ye who believe) in Muhammad and the Qur'an! (Take your precautions) against your enemy and do not advance dispersed, (then advance the proven ones) then put forward the ones that are the best, (or advance all together) with your Prophet.