let sleeping dog lie 别惹事生非；别自找麻烦；不必打草惊蛇

【例句】
Don't mention George's name to Roger. They had a falling out two years ago. Let sleeping dogs lie, if you know what I mean.
对罗杰别提乔治，他们两年前大吵了一架。依我看，最好不要惹是生非。

It might have been perfectly innocent, So you just let sleeping dogs lie.
也许他们根本就没什么，所以你还是别惹麻烦。