Surah 2:279
"If you do not, be on notice of war from God and His messenger. But if you turn (in repentance), you will have your principal. You will not have committed evil or been done evil."
2.279 – be on notice of war from Allah and His messenger
The practice of usury (taking interest for loans) is forbidden in verse 278, but this verse backs up the prohibition with the threat of war.
- from The Quran with Christian Commentary: A Guide to Understanding the Scripture of Islam