The "prosperity gospel" was invented in the latter half of the 20th century by Mammon-loving preachers who had to find some "Scriptural" explanation to justify their extravagant lifestyles and the immense amount of wealth that they had accumulated from the tithes and offerings of their "devotees." So they hunted up Old Testament promises that God had given to Israel and began to proclaim those promises as the unfailing mark of God's blessing today.