Ali 'Imran · 3:154

154. Then He sent down on you, after the pain and distress, peace and security. A group among you, who trusted in the promise of Allah, became overcome by sleep because of the peace and serenity in their hearts. Another group were not blessed with security or sleep, and they were the hypocrites, who only worried about their own safety, and felt upset and scared. They thought badly of Allah, thinking that He would not help His Prophet or support His servants, like those of the time of ignorance before Islam did, who did not understand Allah’s reality. These hypocrites said, due to their ignorance of Allah, that they did not have a say in whether they went out to fight; and if they had, they would not have done so. Tell them, O Prophet, in reply, that everything that happens is up to Allah, and that He decreed that they would go out to fight. These hypocrites hide in themselves doubt and bad opinion which they do not show to you, saying that if they had a say in whether they had gone to fight, then people would not have been killed in this place. Tell them, O Prophet, in reply, that if they had been in their houses far from the places of battle and death, those whom Allah had destined to be killed would inevitably go out to the places of their death. Allah only did this to test the intentions and motives in your hearts, and to reveal the faith and hypocrisy in them. Allah knows what is in the hearts of people, and nothing is hidden from Him.