"People may cover their hatred with pleasant words,
but they're deceiving you.
They pretend to be kind, but don't believe them.
Their hearts are full of many evils.
While their hatred may be concealed by trickery,
their wrongdoing will be exposed in public."
We are to be discerning and not naïve about people. Some people are deceptive. Proverbs suggests that we need to give people time for their true character to come out. When considering working with someone, or any kind of long-term relationship, you have to take your time so you can discern their true character. This passage suggests that any deception will come to light.