From the day envy was discovered, problems started between people. That's why God made the Day of Judgment, because humans are weak in the face of worldly desires, and Satan exploited this weakness and pushes people towards hatred.
ﻣﻦ ﻳﻮﻡ ﺍﻛﺘﺸﻒ ﺍﻟﺤﺴﺪ ﺍﺑﺘﺪﺍﺕ ﺍﻟﻤﺸﺎﻛﻞ ﺑﻴﻦ ﺍﻹﻧﺴﺎﻥ ﻟﻬﺪﺍ ﷲ ﺟﻌﻞ ﻳﻮﻡ ﺍﻟﺤﺴﺎﺏ ﻻﻥ ﺍﻹﻧﺴﺎﻥ ﺿﻌﻴﻒ ﺃﻣﺎﻡ ﺷﻬﻮﺍﺕ ﺍﻟﺪﻧﻴﺎ ﻭ ﺍﻟﺸﻴﻄﺎﻥ ﺍﺳﺘﻐﻞ ﻫﺪﺍ ﺍﻟﻀﻌﻒ ﻭ ﻳﺪﻓﻊ ﺍﻹﻧﺴﺎﻥ ﻟﻠﺤﻘﺪ