I want someone on Instagram to give the code from his eShop Card for free, what should I do?

On Instagram, someone wrote to me, who wants to give me a Nintendo eShop Card just like that. He also sent me a picture. You did not see the code yet, because you have to scratch first. If I say yes and he sends me the code, thanks maybe get a virus or something? Sounds silly, but why should a stranger just give me his code like that?

If he really is a stranger I would just ignore it, because it seems very funny to me. Even people I only know via the Internet have already given me things, but if you do not know someone, it is hidden behind them with a not-so-small probability of another person's intention.

Many thanks for the answer!