Overall meaning : Allah forbids the faithful from following the example of the unbelievers, who, objecting to Allah’s decree, say of their brothers who die after having set out on a journey for trade purposes to faraway places or are killed after having gone forth to war, ‘Had they stayed with us in our homeland, they would not have died, nor would they have been killed.’ Thus, Allah makes such thoughts and statements the cause of deep and bitter regret in their hearts. For in truth it is Allah alone who gives life and causes death, all by His will, and a person dies only when his lifespan expires, and He, Exalted be He, sees everything His creatures do.
Allah Almighty then informs His servants that those who are killed or die in His cause will surely attain His grace and mercy, which are far better for them than staying in this world and vastly superior to all the worldly riches people amass, reminding them that whether they die or are killed, it is to Him alone that they will all be returned.