This question already has an answer here:
What's the protocol for the situation where somebody asks a good, valid, on-topic question, and I have a (non-StackExchange) link which answers their question perfectly?
Comments are for requesting clarification, and link-only answers are out. I've also seen it mentioned a few times that replicating content already on other websites isn't cricket.
So what's the deal? Should I just leave it and assume that if I can find it, the OP can find it also? Or is putting that link into a comment OK?