In Islam the both material and spiritual life as well as the personal and social life are never separated meaning the true believer is the one who cares about all his religious duties including saying prayer, remembering God, personal behavior, etc as well as not ignoring his social duties such as charity, observing human rights, booty, etc.
Therefore spending wealth refers to the true belief, as the following verses of the Noble Koran indicate:
1. Believers are merely those whose hearts feel wary whenever God is mentioned and whose faith increases when his verses are recited to them. On their Lord do they rely. Those who keep up prayer and spend whatever we have provided them with are truly believers. They hold rank before their Lord, as well as forgiveness and generous provision. (Booty/18:2-4)
2. You who believer, do not cancel you acts of charity by [making] any reproach or scolding like someone who spends his money simply for people to see it while he does not believe in God and the Last Day. (2:264)
3.Tell My servant who believe to keep up prayer and spend what we have provided them with both secretly and openly before a day comes along when there will be no bartering nor any intimacy.(14:31)
4. The only ones who believe in our signs are those who drop drown kneeling [in worship] whenever they are reminded of them, and hymn their Lord praise.
They do not act so proudly. They slip quietly away from their beds to appeal to their Lord: in fear and anticipation, and spend [charitably] whatever we have provided them with. (32:15-16)