Proverbs 24:9

The thought of foolishness is sin - חטאת אולת זמת zimmath ivveleth chattath . "The device of folly is transgression;" or, "an evil purpose is sinful;" or, perhaps more literally, "the device of the foolish is sin." It has been variously understood by the versions.

"The cunning: of the fool is sin."

- Targum.