What word finishes the idiom Let sleeping dogs?

The idiom is: Let sleeping dogs lie.

It means, don't aggravate a person or situation when it is already calm or calmed down.

Example:

"I hate her," Julie fumed three days after a girl insulted her at school. "I'll show her!"

"The principal already took care of the problem," her mother counseled. "She has been expelled for a week and won't be bothering you again--let sleeping dogs lie."

"The welfare office took away $50 in food stamps!"

"Yes, but they didn't make you re-pay them when you earned $300 from your job. It might be better to let sleeping dogs lie."

NOTE 1: The Word dogs refer to dogs, not that you are calling someone a dog.

NOTE 2: The Word lie, here, means a sleeping dog, and does not mean a person as a liar.

One origin of this idiom is that a dog can be cranky when abruptly awoken, and can attack. So it is better to not disturb the dog.