"Allah will deprive usury of all blessing, but will give increase for deeds of charity" (Quran 2: 276).
Narrated Jabir ibn Abdullah(r.a.): Allah's Messenger(sallallahu alaiyhi wasallam) cursed the accepter of interest and its payer, and one who records it, and the two witnesses; and he said: They are all equal (Muslim).
Abu Huraira(r.a.) related that the Prophet(sallallahu alaiyhi wasallam) said: On the night of the Miraj I came upon a group of people whose bellies were like houses. They were full of snakes which could be seen from outside their bellies. I asked Gabriel who they were, and he told me that they were the people who had practiced Riba (Interest). (Ahmad, Ibn Maja)
Abdullah ibn Hanjalah(r.a.) related that the Prophet(sallallahu alaiyhi wasallam) said: A dirham of Riba (interest) knowingly taken by a man is a sin worse than committing Zina (fornication) 36 times (Ahmad, Daraqutni).