lay a finger on

加害
A:I'm really pissed.
A:真是气死我了。
B:Why? Tell me what's the matter.
B：怎么啦?给我说说看。
A:I am angry with Tom again.
A：汤姆又惹我生气了。
B:Why do you often get angry with Tom?
B：你为什么老生他的气?
A:He always makes mistakes.
A:他总是犯错误。
B:After all, he is only a child. If you lay a finger on him, I'll leave you.
B：他毕竟还是个孩子，你要动他一根毫毛，我就离开你。