Qur'an 4:102

وَإِذَا كُنتَ فِيهِمْ فَأَقَمْتَ لَهُمُ ٱلصَّلَوٰةَ فَلْتَقُمْ طَآئِفَةٌ مِّنْهُم مَّعَكَ وَلْيَأْخُذُوٓا۟ أَسْلِحَتَهُمْ فَإِذَا سَجَدُوا۟ فَلْيَكُونُوا۟ مِن وَرَآئِكُمْ وَلْتَأْتِ طَآئِفَةٌ أُخْرَىٰ لَمْ يُصَلُّوا۟ فَلْيُصَلُّوا۟ مَعَكَ وَلْيَأْخُذُوا۟ حِذْرَهُمْ وَأَسْلِحَتَهُمْ ۗ وَدَّ ٱلَّذِينَ كَفَرُوا۟ لَوْ تَغْفُلُونَ عَنْ أَسْلِحَتِكُمْ وَأَمْتِعَتِكُمْ فَيَمِيلُونَ عَلَيْكُم مَّيْلَةً وَٰحِدَةً ۚ وَلَا جُنَاحَ عَلَيْكُمْ إِن كَانَ بِكُمْ أَذًى مِّن مَّطَرٍ أَوْ كُنتُم مَّرْضَىٰٓ أَن تَضَعُوٓا۟ أَسْلِحَتَكُمْ ۖ وَخُذُوا۟ حِذْرَكُمْ ۗ إِنَّ ٱللَّهَ أَعَدَّ لِلْكَـٰفِرِينَ عَذَابًا مُّهِينًا

“And when you [i.e., the commander of an army] are among them and lead them in prayer, 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.”

An-Nisaa 4:102 · Saheeh International