【英语时差8,16】不）动…一根汗毛；（不）对…动手

This idiom is always presented in a negative way, and most often as a threat. If a person is physically¹ violent, he or she may hit, slap or punch others, using his entire hand. What this idiom is saying to such a person is that using even one finger in an aggressive manner is unacceptable. To "lay a finger on" simply means to touch. So, this idiom is a warning that any physical action whatsoever—even a gentle touch —will not be tolerated. For example, we can imagine two people arguing, and one of them becoming so frustrated² that he wants to hit or break something. That is the kind of situation where the second person might speak this idiom to the frustrated one, warning that he'd better limit his aggression³ to words only, and never touch.

1 physically   

adj.物质上，体格上，身体上，按自然规律

参考例句：

• He was out of sorts physically,as well as disordered mentally.他浑身不舒服，心绪也很乱。
• Every time I think about it I feel physically sick.一想起那件事我就感到极恶心。

2 frustrated   

adj.挫败的，失意的，泄气的v.使不成功( frustrate的过去式和过去分词 )；挫败；使受挫折；令人沮丧

参考例句：

• It's very easy to get frustrated in this job. 这个工作很容易令人懊恼。
• The bad weather frustrated all our hopes of going out. 恶劣的天气破坏了我们出行的愿望。 来自《简明英汉词典》

3 aggression   

n.进攻，侵略，侵犯，侵害

参考例句：

• So long as we are firmly united, we need fear no aggression.只要我们紧密地团结，就不必惧怕外来侵略。
• Her view is that aggression is part of human nature.她认为攻击性是人类本性的一部份。