“Adam” is not only “a man”; it is the name of the first human being. Says Rashi, “Adam did not offer a sacrifice of anything stolen since everything was his; similarly when you bring an offering to God it must not be something which was stolen”.
There is a verse in Isaiah that probably inspires this comment: Isa. 61:8, which says that God “hates robbery in offerings”. The person who wants to show God how much he loves Him may be tempted to take something which isn’t his and bring it to the sanctuary. What we are being told by Isaiah, Rashi and Jewish tradition as a whole is that your religiosity is no excuse for acting unethically.
A modern example might be a person who acquires assets by questionable means and seeks to whitewash himself by using them for a big donation to the synagogue. Maybe he thinks no-one will ever find out, but he has forgotten that God sees and notes everything… and if God cannot possibly condone the act of dishonesty that lies behind the donation, the putative donor dare not quieten his conscience and imagine that the end justifies the means.