An-Nisaa 4:102

When you [O Prophet] are with them and lead them in prayer, let a group of them stand [in prayer] with you, carrying their weapons. When they have finished their prostration, let them take their positions in the rear. Then let the other group that has not yet prayed join you in prayer, keeping vigilant and carrying their arms[75]. The disbelievers wish that you would neglect your weapons and belongings, so they could launch on you a surprise attack. But there is no blame on you if you lay down your weapons because of the inconvenience of rain or because you are ill, but take all precautions. Indeed, Allah has prepared for the disbelievers a humiliating punishment.

[75] This is the manner of prayer in danger on the battlefield.

And when you [i.e., the commander of an army] are among them and lead them in prayer,[217] let a group of them stand [in prayer] with you and let them carry their arms. And when they have prostrated, let them be [in position] behind you and have the other group come forward which has not [yet] prayed and let them pray with you, taking precaution and carrying their arms. Those who disbelieve wish that you would neglect your weapons and your baggage so they could come down upon you in one [single] attack. But there is no blame upon you, if you are troubled by rain or are ill, for putting down your arms, but take precaution. Indeed, Allāh has prepared for the disbelievers a humiliating punishment.

[217] At times of fear on the battleground.

102. When you (O Messenger Muhammad صلى الله عليه وسلم) are among them, and lead them in As-Salât (the prayer), let one party of them stand up [in Salât (prayer)] with you taking their arms with them; when they finish their prostrations, let them take their positions in the rear and let the other party come up which have not yet prayed, and let them pray with you taking all the precautions and bearing arms. Those who disbelieve wish, if you were negligent of your arms and your baggage, to attack you in a single rush, but there is no sin on you if you put away your arms because of the inconvenience of rain or because you are ill, but take every precaution for yourselves. Verily, Allâh has prepared a humiliating torment for the disbelievers.[32]

[32] (V.4:102) See the footnote of (V.2:239).

And when thou (O Muhammad) art among them and arrangest (their) worship for them, let only a party of them stand with thee (to worship) and let them take their arms. Then when they have performed their prostrations let them fall to the rear and let another party come that hath not worshipped and let them worship with thee, and let them take their precaution and their arms. Those who disbelieve long for you to neglect your arms and your baggage that they may attack you once for all. It is no sin for you to lay aside your arms, if rain impedeth you or ye are sick. But take your precaution. Lo! Allah prepareth for the disbelievers shameful punishment.