"God Sent an Evil Spirit"

The Concordia Self-Study Bible has a footnote which is helpful for understanding Judges 9:23 where it says, "God sent an evil spirit between Abimilech and the citizens of Shechem, who acted treacherously against Abimilech." Regarding the use of "evil spirit," it says, "Perhaps a spirit of distrust or bitterness. The Hebrew for 'spirit' is often used to describe an attitude or disposition." The People's Bible says, "God sends such spirits when he withdraws his grace and allows Satan and his unholy allies free reins in the affairs of men." However it is interpreted, we know that God does not cause evil but he does allow it at times to carry out his will.