This is a deed whose doers have been warned by the Qura’n about the chastisement in Hell. In verse 275 of Surah Baqarah it says:
“Whoever desists shall have what he has earned earlier as his own and his affairs rest with God but those who turn their backs (and keep doing it) will be the ones in the fire and there they shall abide for ever.”
There is a similar meaning in verses 130 and 131` of Surah Al Imran admonishing the usurers about Hell:
“O believers! Do not devour usury doubling it over, and take refuge in God that you may be successful.131. And fear the fire that is prepared for the disbelievers.”
When the usurers declared war against God or He declared war on them they became disbelievers. This is a very terrifying statement about this great sin.
We learn from certain hadiths that usury was banned in all the divine books as stated in Fiq-ar-Reza: (1)