Teaching or giving advice without mentioning the Buddha

Sometimes I see perfect situations to teach something from the Buddha and help someone with it, impermanence, worldly concerns, etc... however some people will immediately shut down and not listen if they know it was spoken by the Buddha... still I want to help. So I try to focus on the teachings that can benefit them without saying in a explicit way it came from Buddhism (of course I do not say the teaching was mine as well, I just don't mention the source or say it is something I learned...) Is that wrong, unethical or a cause for bad Karma? I have never thought about it!