give (someone) the back of (one's) hand
1. To strike someone with the backside of one's open hand. Son, I'll give you the back of my hand if you ever speak to your mother that way again.
2. To reject, snub, or rebuke someone; to display to someone a show of contempt, scorn, or rejection. I'll give the back of my hand to anyone who says I'm not a good parent. He pleaded to be forgiven by his wife, but she merely gave him the back of her hand.