Overall meaning : Allah commands the believers to hasten to go into battle to fight against the unbelievers, lightly armed or heavily armed, and to strive with their wealth and their lives to make Allah’s religion reign supreme, for this will be better for them, if only they knew the virtue of fighting in Allah’s cause and the superiority and merits of those who engage in it.
Allah then addresses His Prophet Muhammad, may Allah bless him and grant him peace, saying: Had there been a prospect of a booty close at hand and an easy journey to a place right on the doorstep, the hypocrites who had chosen not to take part in fighting the Romans, would have definitely gone forth with you, but nevertheless they considered the travelling distance to the northern borders to fight the Romans and the rather extreme hardship this would involve too great for them, and so they resolved to stay behind. They will falsely swear to you, Muhammad, saying, ‘We swear by Allah that we would have surely gone out with you to fight had we been able to do so,’ thus only incurring Allah’s wrath due to their hypocrisy and false oaths, and Allah knows that they are certainly lying.
Allah has pardoned you, Muhammad, for permitting these hypocrites to stay behind when they asked you to exempt them from going forth with you. Why did you give them permission? You should not have given them leave until you had known for certain those who spoke the truth and offered legitimate excuses and the liars who had no legitimate excuses whatsoever.