Quran 49:12

“O you who believe! Avoid much suspicion, indeed some suspicions are sins. And spy not, neither backbite one another. Would one of you like to eat the flesh of his dead brother? You would hate it (so hate backbiting). And fear God. Verily, God is the One Who accepts repentance, Most Merciful.” - The Religion of Islam - Respect (part 1 of 3)