According to a forum post I found when googling this quote, this was said by Josef Stalin on April 6th, 1948. Googling the quote presents a number of outher results as well, all of which are not really credible sources.
My usual search engine for credible sources, http://scholar.google.com/ has nothing either, so I'm asking you guys. Did he really say it? I'm skepical myself.
It is very widely quoted, but much harder to pin down. While I don't have the original source, nor could I read Finnish to verify it if I did, I found it cited as a quote recounted by Finnish Lt. General Oinonen in 1971, for "Sotilasaikakauslehti" (Finnish: "Military Magazine") as a statement of Stalin at a post-war diplomatic meeting of Soviet and Finnish military personnel.
The full quote appears to have had a couple more words, and would explain why Lt. Gen Oinonen remembered it: "No-one respects a country with a poor army. All respect a country with a good army. I raise my toast to the Finnish Army and the representatives of it here, General Heinrichs and General Oinonen."
Apologies that I'm making a top level reply without source in hand, but hopefully this citation is helpful for somebody who does have access to that magazine, and the ability to read it, to verify either way. Given what could be perceived as the self-aggrandizing nature of the statement if that context proves correct, I don't know if that would actually prove anything about it being said, but it would at least provide a basis for the popular existence of the quote.