Nor should the Believers all go forth together: if a contingent from every expedition remained behind, they could devote themselves to studies in religion, and admonish the people when they return to them,- that thus they (may learn) to guard themselves (against evil). (9:122)

No blame is there on the blind, nor is there blame on the lame, nor on one ill (if he joins not the war): But he that obeys God and his Apostle,- (God) will admit him to Gardens beneath which rivers flow; and he who turns back, (God) will punish him with a grievous Penalty. (48:17)