Every person earns money. There are two categories of expenditure of this money.  One is israf, and the other is zakat. Israf means to waste money. All the money spent is wasted if it is used for buying worldly things: to make profit in this world, enjoy fame, be popular in the eyes of the world and to fulfil your desires here.

Spending money for all this is israf, or wastage. It is wastage because the profits of this world cannot be had in the Hereafter. The criterion by which God judges an action is whether it would have any value in the next eternal world.  The Quran says: إِنَّ هَؤُلَاءِ يُحِبُّونَ الْعَاجِلَةَ وَيَذَرُونَ وَرَاءَهُمْ يَوْمًا ثَقِيلًا (76.27)

People are totally trapped in the temporary period of this life. This is the basis of all their activities. They are not concerned with greater success of the eternal life. They don’t spend their energy or capacity for the life of next world.

Here we need to understand zakat. What is the meaning of zakat? The literal meaning of zakat is to increase, to flourish, to grow. The money we spent in God's cause is called zakat. This is why, it grows. What is the meaning of growth or increase? It will have benefits from this world to the world Hereafter. You spent money in this world, but it increased to the extent that its effects reach the Hereafter. After death, this money will be available to you in the form of Paradise in the life Hereafter. This will be the eternal reward. This is why, zakat means growth. The money you spend to fulfil your desires is called wastage in the Quran. (17.27) The money you spend to please God is called growth. It will grow and benefit you even in the life Hereafter.