How can you expect to find ivory in a dog’s mouth?

Similar sayings:

Out of a dog’s mouth will never come ivory tusks Out of a dog’s mouth will never come ivory tusks
You can’t expect both ends of a sugar cane to be as sweet You can’t expect both ends of a sugar cane to be as sweet
All people are your relatives, therefore expect only trouble from them All people are your relatives, therefore expect only trouble from them
Look for a thing until you find it and you’ll not lose your labor Look for a thing until you find it and you’ll not lose your labor
The man who wakes up and finds himself famous hasn’t been asleep The man who wakes up and finds himself famous hasn’t been asleep

Chinese sayings and proverbs