There should be no misgivings about the veracity of the statement, "out of what We have given you," for Allah is the one who gives sustenance to mankind. Man comes empty handed in this world from his mother's womb, and leaves empty handed when he is put in the grave. The wealth and the treasures of this world belong to the one who has created them. If someone earns wealth, it is because of Allah's grace, for if He had not given him the intelligence and capabilities to do so, he would have been helpless. Quite often we observe that some very intelligent people remain poor, while people with ordinary capabilities become wealthy. I have myself observed this very frequently. When Allah wants to take away some one's wealth then no capability, or skill can assist him. We can therefore conclude that whatever is given to mankind is out of Allah's grace. In addition, the purpose for which Allah enjoins the spending of wealth is the best way in which wealth can be spent, i.e., the defense and propagation of truth.