The Hebrew word mamin means 'the one believing'. See Deut 1:32 for the plural form. מאמינם.and the singular in Is 28:16 מאמין No man can serve God and himself.
Mt 6:25 ¶ Therefore I say unto you, Take no thought for your life, what ye shall eat, or what ye shall drink; nor yet for your body, what ye shall put on. Is not the life more than meat, and the body than raiment?
The root nature of original sin is that man makes himself out to be a god. He places his own interests first, and makes his own rules for good and evil. The opposition to God is not devils demons or money. It is the self. You cannot serve God and self.
He does not conclude by saying "Take no thought for what is in your pocket, purse or bank account". He addresses the objects that the instinctive nature of man places first: life, food, drink, clothing. These are the things that even the believer is tempted to put before God because of our sinful flesh.
Luke 16:9