Will God accept the fast of one who possesses investment certificates and speculates in the shares of usurious banks, and is he thereby considered a usurer?

Allah Almighty has forbidden usury, and those who consume it are the cause of the Muslims' humiliation and abasement. The fast of one who commits a major sin, such as buying shares in usurious banks, is valid, but it is deficient and he may not receive the reward for fasting, because the wisdom behind fasting is to fear Allah by abandoning forbidden acts, and "whoever does not abandon false speech and acting upon it, Allah has no need for him to abandon his food and drink." The purpose of fasting is not hunger and thirst, but rather to break desires and subdue the inciting self, otherwise Allah will not look upon it with acceptance.