Quran 2:278 — The Heifer (Al-Baqarah)

O you who believe, you shall observe GOD and refrain from all kinds of usury, if you are believers.

[2:277] Those who believe and lead a righteous life, and observe the Contact Prayers (Salat), and give the obligatory charity (Zakat), they receive their recompense from their Lord; they will have nothing to fear, nor will they grieve.

[2:279] If you do not, then expect a war from GOD and His messenger. But if you repent, you may keep your capitals, without inflicting injustice, or incurring injustice.