expression, godan verb (-su)
wake a sleeping dog; disturb the water; stir up trouble
Idiomatic expression meaning to bring up an issue that is better left alone, or to stir up unnecessary trouble. The literal meaning is 'to wake a sleeping child'.
その話は寝た子を起こすようなものだ。
That topic is like waking a sleeping dog.
彼は
He deliberately said something that stirred up trouble.