Those who were left behind were glad on account of their sitting behind Allah's Messenger and they were averse from striving m Allah's way with their property and their persons, and said: Do not go forth in the heat. Say: The fire of hell is much severe in heat. Would that they understood (it).

It did not beseem the people of Medina and those round about them of the dwellers of the desert to remain behind the Messenger of Allah, nor should they desire (anything) for themselves in preference to him; this is because there afflicts them not thirst or fatigue or hunger in Allah's way, nor do they tread a path which enrages the unbelievers, nor do they attain from the enemy what they attain, but a good work is written down to them on account of it; surely Allah does not waste the reward of the doers of good;

The believers are only those who believe in Allah and His Messenger then they doubt not and struggle hard with their wealth and their lives in the way of Allah; they are the truthful ones.

You shall believe in Allah and His Messenger, and struggle hard in Allah's way with your property and your lives; that is better for you, did you but know!