A believer should fast not for any worldly benefit, but solely because it is commanded by Allah and in the hope of attaining His pleasure. Indeed, fasting brings many physical and social benefits, yet the believer observes the fast not for these benefits, but purely in obedience to Allah’s command.
It must be remembered that the true reward of worship is spiritual and eternal—its ultimate benefit will be seen in the Hereafter. Although certain acts of worship may also bring worldly advantages, these can never be the reason or the ultimate purpose for performing them.