lay a finger on somebody

lay a finger on (someone or something)

To touch someone or something in the slightest way. If you so much as lay a finger on my son again, I'm calling the cops. I can't believe the vase shattered like that—I feel like I barely laid a finger on it.
See also: finger, lay, on

lay a ˈfinger on somebody

(informal) (often in negative sentences) touch somebody with the intention of hurting them physically: If you lay a finger on her, I’ll call the police.
See also: finger, lay, on, somebody