4:102
And when you are among them and you lead for them the prayer, then let stand a group of them with you and let them take their arms. Then when they have prostrated, then let them be from behind you and let come (forward) a group - other, (which has) not prayed, and let them pray with you and let them take their precautions and their arms. Wished those who disbelieved if you neglect [about] your arms and your baggage so (that) they (can) assault [upon] you (in) an attack, single. But (there is) no blame upon you if was with you any trouble (because) of rain or you are sick that you lay down your arms, but take your precautions. Indeed, Allah has prepared for the disbelievers a punishment humiliating.