Responsibility for the use of money of illegal origin

I'm now wondering, what if, for example, I pay off a mortgage or other large loan in cash, and one of my relatives gives me this money, but I don't know exactly where the money comes from — could I have problems with the law due to possible money laundering? How does Ukraine control the origin of money for such payments, and what is the responsibility if it turns out that the money was obtained illegally, even if I didn't know about it?