9-122
And it is not (proper) for the believers that they should go out all together (to fight), so why not a group go out from every party among them, so that (those who remain behind) could develop sound understanding in religion and (through this religious knowledge) warn their people when they return to them (from war) so that they (too) could be cautious. (R 15)
If all the male members go out to fight, elderly men, women and children will be left unguarded. Besides, in any country men are involved in the supply of essential services like, water, electricity, food etc., therefore some men will have to remain in the city. Those who go out will be engaged in fighting but those who remain at home can find time to acquire knowledge of Islam and pass it on to their brotheren when they return from war.
9-124
And whenever a chapter (of the Quran) is sent down, then from among them is he who says, “”Which of you has this (chapter of the Quran) increased in belief?”” So, as for those who believe, it has (further) increased them in belief and they rejoice.
The Quran increases the intensity of belief of the believers and uncleanliness of the infidels.
9-126
Do they not see that they are afflicted once or twice every year, even then, they neither repent nor are they mindful.
Inspite of being afflicted once or twice a year the infidels are not mindful.
9-127
And whenever a chapter (of the Quran) is sent down, some of them look at others, (as if saying), “”Does anyone see you?”” Then they turn away. Allah has turned away their hearts because they are a people who do not understand.
Those who are infidels, they turn away from The Quran.
9-128
There has come to you a messenger from among yourselves, grievous to him is your distress, (he is) excessively desirous for your (good) and full of pity and merciful to the believers.
The excellent qualities of Prophet Muhammed (PBH) are described and he is advised to declare his trust in Allah (SWT).