If you lie down with dogs, you'll get up/rise with fleas
Idiomatic translations of "If you lie down with dogs..."
Meanings of "If you lie down with dogs..."
The fleas are parasites with no benefits to the dog.
When you hang out with bad people you take up their traits. If they are criminals, drug abusers, etc.. Soon you will be the same. That's why parents don't want their kids to befriend others with bad influences.