In Quran 7:27 Allah SWT states
Pickthall: "O Children of Adam! Let not Satan seduce you as he caused your (first) parents to go forth from the Garden and tore off from them their robe (of innocence) that he might manifest their shame to them. Lo! he seeth you, he and his tribe, from whence ye see him not. Lo! We have made the devils protecting friends for those who believe not."
Why does Allah Almighty assign devils to those who disbelieve in Allah's revelations?